Reconfigurable multi-channel WDM drop module using a tunable wavelength-selective photodetector array

doi:10.1364/OE.18.005879

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Reconfigurable multi-channel WDM drop module using a tunable wavelength-selective photodetector array

Xiaofeng Duan, Yongqing Huang, Xiaomin Ren, Hui Huang, Sanxian Xie, Qi Wang, and Shiwei Cai »View Author Affiliations

Optics Express, Vol. 18, Issue 6, pp. 5879-5889 (2010)
http://dx.doi.org/10.1364/OE.18.005879

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▸ Article Outline
– Abstract
1. Introduction
2. Design and fabrication
3. Results and discussion
4. Conclusion
– References and links

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Abstract

An integrated reconfigurable four-channel wavelength-division-multiplexed drop module for use in the long-wavelength was demonstrated using a tunable wavelength-selective photodetector array. The array consists of an InP-based p-i-n absorption structure and a GaAs-based multistep Fabry-Pérot filtering cavity. The high quality GaAs/InP heteroepitaxy was realized by employing a thin low temperature buffer layer. The GaAs-based multistep cavity was fabricated by wet etching and regrowth. The dropped central wavelengths were 1538, 1550, 1559, and 1570nm. The tunable range reached 10nm with a tuning power efficiency of 14.2nm/W. A spectral linewidth less than 0.5nm (FWHM), a 3dB bandwidth of 9.2GHz, and the peak quantum efficiencies from 13% to 20% were simultaneously obtained, in agreement with the theoretical simulation.

1. Introduction

Tunable wavelength-selective photodetector (WSPD) arrays around 1550nm will be important for the development of the reconfigurable optical add-drop multiplexer (ROADM). Thus far, several ROADMs based on integrated wavelength demultiplexers, such as the tapered Fabry-Pérot (F-P) filters [1

B. Pezeshki, F. K. Tong, J. A. Kash, D. W. Kisker, and R. M. Potemski, “Tapered Fabry-Pérot waveguide optical demultiplexer,” IEEE Photon. Technol. Lett. 5(9), 1082–1085 (1993). [CrossRef]

B. Pezeshki, F. F. Tong, J. A. Kash, and D. W. Kisker, “Vertical cavity devices as wavelength selective waveguides,” J. Lightwave Technol. 12(10), 1791–1801 (1994). [CrossRef]

], microring resonator filters [3

K. Takahashi, Y. Kanamori, Y. Kokubun, and K. Hane, “A wavelength-selective add-drop switch using silicon microring resonator with a submicron-comb electrostatic actuator,” Opt. Express 16(19), 14421–14428 (2008), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-16-19-14421. [CrossRef] [PubMed]

–5

J. Takayesu, M. Hochberg, T. Baehr-Jones, E. Chan, P. Guangxi Wang, Sullivan, J. Yi Liao, L. Davies, A. Dalton, Scherer, and W. Krug, “A Hybrid Electrooptic Microring Resonator-Based $1 \times 4\times 1$ ROADM for Wafer Scale Optical Interconnects,” J. Lightwave Technol. 27(4), 440–448 (2009). [CrossRef]

], and array waveguide gratings (AWGs) [6

K. T. Shiu, S. S. Agashe, and S. R. Forrest, “An InP-based monolithically integrated reconfigurable optical add-drop multiplexer,” IEEE Photon. Technol. Lett. 19(19), 1445–1447 (2007). [CrossRef]

C. G. M. Vreeburg, T. Uitterdijk, Y. S. Oei, M. K. Smit, F. H. Groen, E. G. Metaal, P. Demeester, and H. J. Frankena, “First InP-based reconfigurable integrated add-drop multiplexer,” IEEE Photon. Technol. Lett. 9(2), 188–190 (1997). [CrossRef]

], have been proposed and demonstrated. However, discrete photodetectors are needed for the scheme of the tapered F-P filters, the precise control of the coupling strength presents practical difficulties for the microring resonator filters, and the manufacture process is complicated and costly for the AWGs scheme.

In order to achieve large-scale integration and reduce manufacturing cost, it is desirable to develop an integrated long-wavelength tunable WSPD array for multi-wavelength receiving applications. By integrating an InP-based p-i-n absorption structure (PIN) with a GaAs-based multistep F-P filtering cavity (FPC), the tunable WSPD array is realizable and a small optical bandwidth, a large tuning range and a high speed can be attained. To our knowledge, there is still no report on the photodetector array based on the multistep FPC. In addition, by utilizing a tapered glass optical waveguide, the array can be used as an integrated reconfigurable multi-channel wavelength-division-multiplexed (WDM) drop module. The signal input from the fiber is coupled to the input port of the tapered glass. The light propagating in the waveguide is demultiplexed by the multistep FPC and routed to the corresponding PIN photodetectors.

The paper reports our work on design, fabrication, and testing of an integrated reconfigurable four-channel WDM drop module based on the tunable WSPD array, which operates at 1538, 1550, 1559, and 1570 nm. Each photodetector of the array can be tuned respectively, and the tunable range is about 10nm. A spectral linewidth less than 0.5nm (FWHM), a 3dB bandwidth of 9.2GHz, and the peak quantum efficiencies from 13% to 20% were obtained, in agreement with the theoretical simulation.

2. Design and fabrication

2.1 Modeling of the integrated reconfigurable four-channel WDM drop module

The schematic structures of the reconfigurable four-channel WDM drop module and a tunable WSPD of the array are shown in Fig. 1 . Figure 1(b) is the proposed structure of the WSPD, which combines an InP-based PIN photodetector array with a GaAs-based multistep FPC. The GaAs-based multistep FPC comprises two identical distributed Bragg reflectors (DBRs) and a GaAs multistep resonator cavity layer. The top and bottom DBRs are made of GaAs/AlGaAs quarter-wave stacks designed for high reflectivity at 1550nm center wavelength. Each step height of the GaAs multistep resonator cavity layer is about 20nm, for the wavelength interval of the spectral responses is about 10nm. The device can be fabricated by GaAs/InP heteroepitaxy growth of an InP-based PIN photodetector array on a GaAs/AlGaAs multistep FPC. The high quality GaAs/InP heteroepitaxy is realizable by employing a thin low temperature buffer layer [8

H. Huang, X. Ren, J. Lv, Q. Wang, H. Song, S. Cai, Y. Huang, and B. Qu, “Crack-free GaAs epitaxy on Si by using midpatterned growth: Application to Si-based wavelength-selective photodetector,” J. Appl. Phys. 104(11), 113114 (2008). [CrossRef]

–10

X. Duan, Y. Huang, H. Huang, X. Ren, Q. Wang, Y. Shang, X. Ye, and S. Cai, “Monolithically integrated photodetector array with a multistep cavity for multiwavelength receiving applications,” J. Lightwave Technol. 27(21), 4697–4702 (2009). [CrossRef]

]. The high reflecting film is formed by depositing a mirror on the bottom surface of the glass. The glass has two vertical tapers, whose angles are designed to ensure the input beam and output beam perpendicular to the tapers. The array can be bonded onto the tapered glass using the polymer benzocyclobutene (BCB) [11

I. Christiaens, G. Roelkens, K. D. Mesel, D. V. Thourhout, and R. Baets, “Thin-Film Devices Fabricated With Benzocyclobutene Adhesive Wafer Bonding,” J. Lightwave Technol. 23(2), 517–523 (2005). [CrossRef]

]. As shown in Fig. 1(a), The light input from the taper are guided by the FPC and the bottom mirror with low loss, only that meet the resonant condition can pass through the filters and be routed to the corresponding PIN photodetectors. Each photodetector of the array operates at a different wavelength due to the multistep resonator cavity layer, which can be tuned respectively based on the thermal-optic effect [12

V. Passaro, F. Magno, and A. Tsarev, “Investigation of thermo-optic effect and multi-reflector tunable filter/multiplexer in SOI waveguides,” Opt. Express 13(9), 3429–3437 (2005), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-13-9-3429. [CrossRef] [PubMed]

–14

H. Halbritter, F. Riemenschneider, S. Syguda, C. Dhanavantri, M. Strassner, A. Tarraf, B. R. Singh, I. Sagnes, and P. Meissner, “Tunable and wavelength selective pin photodiode,” Electron. Lett. 40(6), 388–390 (2004). [CrossRef]

Fig. 1 (a) Schematic diagram of the integrated reconfigurable four-channel WDM drop module using a tunable WSPD array with a multistep cavity. (b) Structure of the tunable and wavelength selective PIN photodetector.

When the photocarrier generation occurs throughout the device including the contacts, assuming that only those carriers generated in the high electric field i-region can be collected, the quantum efficiency η can be written as [15

M. S. Ünlü and S. Strite, “Resonant cavity enhanced photonic devices,” Appl. Phys. (Berl.) 78, 607–639 (1995). [CrossRef]

η = (1 - R) \cdot e^{- α \cdot d_{p}} \cdot (1 - e^{- α \cdot L})

(1)

where α is the absorption coefficient, d_p is the thickness of the p-type contact layer, L is the thickness of the absorption layer, and R is the reflectivity of the device. The reflectivity of the device is calculated by using the transfer matrix method. E_in⁺ and E_in⁻ denote the upward- and downward-traveling light under the bottom surface; E_out⁺ and E_out⁻ denote the upward- and downward-traveling light above the n-type InP layer, respectively.

(\begin{array}{l} E_{i n}^{+} \\ E_{i n}^{-} \end{array}) = S_{B o t t o m D B R} \cdot U_{C a v i t y} \cdot S_{T o p D B R} \cdot S_{P I N} \cdot (\begin{array}{l} E_{o u t}^{+} \\ E_{o u t}^{-} \end{array}) = S \cdot (\begin{array}{l} E_{o u t}^{+} \\ E_{o u t}^{-} \end{array}) = (\begin{matrix} S_{11} & S_{12} \\ S_{21} & S_{22} \end{matrix}) \cdot (\begin{array}{l} E_{o u t}^{+} \\ E_{o u t}^{-} \end{array})

(2)

where S_BottomDBR, S_TopDBR, S_PIN represent the transfer matrixes of the bottom DBRs, top DBRs and PIN structure, respectively. U_Cavity is the phase transfer matrix of the resonator cavity layer. According to Eq. (2) and the assumption that there is no downward-traveling light from the top of the device, E_out⁻ = 0, E_in⁺ = S₁₁× E_out⁺, and E_in⁻ = S₂₁× E_out⁺. Thus, the reflectivity of the device is given by:

R = {| S_{21} / S_{11} |}^{2}

(3)

Finally, the quantum efficiency of the device was calculated from Eqs. (1) and (3).

The wavelength dependencies of the quantum efficiency are shown in Fig. 2 for different pairs. The three curves correspond to the cases of 5, 10 and 20 pairs DBR. The photodetector exhibits the peak quantum efficiency of 23% regardless of optical loss in the FPC, which is independent of pairs. The FWHM decreases with additional pairs, down to less than 0.3nm over twenty GaAs/AlGaAs pairs. If the reflectivity of the bottom mirror is 99.5%, the calculated spectral responses at the drop port of the integrated reconfigurable four-channel WDM drop module are shown in Fig. 3 , which correspond to different resonator cavity thicknesses.

Fig. 2 Theoretical spectral response characteristics for a GaAs/AlGaAs quarter-wavelength stacks mirror for 5, 10and 20 pairs.

Fig. 3 Theoretical spectral response characteristic at the drop port of the integrated reconfigurable four-channel WDM drop module. The dropped central wavelengths are 1540, 1550, 1560, and 1570nm.

2.2 Growth of the WSPD array

The details of the epitaxial structure used in this work are given in Table 1 . The device was fabricated by growth of an InP-based PIN photodetector array on a GaAs/AlGaAs multistep FPC. The GaAs/AlGaAs multistep FPC comprises two identical DBRs and a GaAs multistep resonator cavity layer. The DBRs are quarter-wave stacks consisting of 22 periods of alternating GaAs and Al_0.9Ga_0.1As layers, and the designed operating wavelength is 1550 nm. The InP-based PIN comprises a 50 nm InGaAs etching-stop layer, a 256 nm n-doped InP layer, a 40 nm InGaAs etching-stop layer, a 468 nm InP spacer layer, a 400 nm InGaAs absorption layer, a 240 nm InP spacer layer, a 200 nm p-doped InGaAs layer, and a 120 nm InP cap layer. The etching-stop layer enables precise deposition of the electrode on the n-doped InP layer during the device fabrication.

Table 1 Layer structure of the device

Material	Doping (cm⁻³)	Thickness (nm)
InP cap layer	Undoped	120
In_0.53Ga_0.47As	p + 1 × 10¹⁹	200
InP	Undoped	240
In_0.53Ga_0.47As absorber layer	Undoped	400
InP	Undoped	468
In_0.53Ga_0.47As	Undoped	40
InP	n + 2 × 10¹⁸	256
In_0.53Ga_0.47As	Undoped	50
InP	Undoped	1272
InP low temperature buffer	Undoped	48
Top GaAs/AlGaAs DBRs (22 pairs)
Multistep resonator cavity layer
Bottom GaAs/AlGaAs DBRs (22 pairs)
Semi-insulating GaAs substrate

The epitaxy was performed by metal-organic chemical vapor deposition (MOCVD) with a Thomas Swan CCS-MOCVD system at a pressure of 100 Torr. Trimethylgallium, trimethylindium, trimethylaluminum, arsine, and phosphine were used as the precursors. Diethylzinc and silane were used as the p-type and the n-type dopant sources, respectively. In this work, the InP and the GaAs substrates were (100)-oriented and epiready grade.

As shown in Fig. 4 , the growth of the WSPD array was carried out as the following steps.

Fig. 4 The growth process of the tunable WSPD array and the fabrication process of the four-step cavity.

(1) 22 pairs of quarter-wave stacks of GaAs/AlGaAs layers (λ₀ = 1550nm) and an 800nm GaAs cavity layer were grown on a semi-insulating GaAs substrate.
(2) The four steps on the epitaxial layer surface of the GaAs cavity are formed by two-step wet etching. The widths of the strip-geometry pattern are 1600μm and 800μm for the first and second photolithography mask, respectively. The patterned sample was etched by H₂SO₄/H₂O₂/H₂O (1:1:30) solution with the etch rate of 1.5nm/s. The first etch depth h₁ is 40nm and the second depth h₂ is 20nm. So each step has a width of 800μm and a step height of 20nm.
(3) After being degreased in organic solvents, another 800nm GaAs cavity layer and 22 pairs of quarter-wave stacks of GaAs/AlGaAs layers were regrown, and then the 48nm InP low temperature buffer layer was grown at 450°C, which realized the high quality GaAs/InP heteroepitaxy growth. The structure of InP-based PIN was grown later. The cross sectional SEM view of the device epitaxial structure is given in the Fig. 5.

Fig. 5 Cross sectional SEM view of the device epitaxial structure.

The double-crystal X-ray diffraction scans of the epitaxial layer are shown in Fig. 6 , in which the left peak B is introduced by the InP-based PIN; the full-width at half-maximum value is 480 arcsec, which indicates the high quality of InP/GaAs heteroepitaxy. The point A shows the influence of the p-type or n-type doping. The right two peaks C and D correspond to the GaAs-based FPC, in which the peak C corresponds to AlGaAs, as its crystal lattice constant is larger than GaAs. The satellite peaks S are contributed to the GaAs/AlGaAs DBRs.

Fig. 6 Double crystal X-ray diffraction ω-2θ scans. The point A shows the influence of the p-type or n-type doping. The right two peaks C and D correspond to the GaAs-based FPC, The satellite peaks S are contributed to the GaAs/AlGaAs DBRs.

2.3 Fabrication of the WSPD array

The device was fabricated as the following procedures. After lithography, Ti-Pt-Au were evaporated and patterned by a lift-off process to form an annular p⁺ Ohmic contact with 30μm inside diameter. A 42μm diameter top round mesa was formed by etching down to the n-type InP contact layer. InP layers and InGaAs layers were selectively removed in HCl/H₃PO₄ (1:1) and H₂SO₄/H₂O₂/H₂O (1:1:2) solution, respectively. The etch rate had been very well controlled by inspecting the test samples. The n⁺ Ohmic contact was achieved by a Pt/Ti/Pt/Au lift-off. Then a 61μm × 64μm bottom square mesa was etched down to the InP buffer layer. The device was covered with Polyimide and annealed at 210°C for passivation. Two windows on the InP buffer layer were opened at both sides of the bottom mesa by standard photolithography and etching, and two holes were then formed by extending the windows vertically down to the GaAs cavity layer of the GaAs-based FPC. Ti/Au was evaporated and patterned by a lift-off process to form electrodes. The device was accomplished after polishing. The optical microscope image of the device is shown in Fig. 7 .

Fig. 7 Optical micrograph of the WSPD array.

2.4 Design of the tapered glass optical waveguide

The input laser beams with different wavelengths from the fiber pigtail are coupled into the tapered glass. The light propagating in the waveguide are demultiplexed by the multistep FPC and routed to the corresponding PIN photodetectors.

The geometry structure of the tapered glass was designed by using the ray optics method. The spacing between the two photodetectors is 800μm, and the thickness of the glass is 5mm. If the taper angle is 4.75°, all the input beams can be assumed to be vertically transferred into the glass waveguide. The 99.5% reflecting film was formed by depositing SiO₂/TiO₂ DBRs on the bottom surface of the glass.

3. Results and discussion

The spectral response measurements were carried out in the 1520-1590nm wavelength range by using an Anritsu Tunics SCL tunable laser with a single-mode fiber pigtail as the light source. An input beam was obtained by collimating the light from the fiber with a fiber collimator.

The spectral response of the device was plotted on a linear scale and a log scale, as shown in Fig. 8(a) and 8(b), respectively. The dropped wavelengths are 1538nm, 1550nm, 1559nm and 1570nm. The right curve corresponds to the as-grown wafer, while others correspond to cumulative recess etches of 20, 40 and 60nm in the FPC, respectively. The spectral linewidth is less than 0.5nm (FWHM) and the peak quantum efficiencies are from 13% to 20% with an extinction ratio of 50dB. The linewidth of the device is mainly dependent on DBR layers. For the narrower linewidth, more pairs of DBR layers are required. The peak quantum efficiency depends mainly on the 400nm In_0.53Ga_0.47As absorber layer and the propagation loss in the tapered glass. The higher quantum efficiency can be achieved by increasing the absorber layer thickness, by using a resonant cavity enhanced (RCE) structure, or by using a one-mirror inclined three-mirror cavity (OMITMC) structure [15

M. S. Ünlü and S. Strite, “Resonant cavity enhanced photonic devices,” Appl. Phys. (Berl.) 78, 607–639 (1995). [CrossRef]

–19

H. Huang, X. Ren, X. Wang, H. Cui, W. Wang, A. Miao, Y. Li, Q. Wang, and Y. Huang, “Theory and experiments of a tunable wavelength-selective photodetector based on a taper cavity,” Appl. Opt. 45(33), 8448–8453 (2006), http://www.opticsinfobase.org/ao/abstract.cfm?URI=ao-45-33-8448. [CrossRef] [PubMed]

Fig. 8 (a) Spectral response at the drop port of the integrated reconfigurable four-channel WDM drop module. The dropped central wavelengths are 1538, 1550, 1559, and 1570nm. (b) Spectral response on a log scale at the drop port of the integrated reconfigurable four-channel WDM drop module, the extinction ratio is 50dB.

The WSPD can be tuned based on quantum-confined Stark effect, carrier-injection effect, thermal-optic effect, or Kerr effect [20

A. Spisser, R. Ledantec, C. Seassal, J. L. Leclercq, T. Benyattou, D. Rondi, R. Blondeau, G. Guillot, and P. Viktorovitch, “Highly selective and widely tunable 1.55-μm InP/air-gap micromachined Fabry-Perot filter for optical communications,” IEEE Photon. Technol. Lett. 10(9), 1259–1261 (1998). [CrossRef]

]. Generally, these effects cannot be considered in isolation, as the thermal-optic effect and the carrier-injection effect. For low injection currents, the carrier-injection effect plays the major role, and a very small blue shift of the wavelength is observed. A large red shift of the wavelength can be obtained with increasing injection currents because the thermal-optic effect predominates [21

M. V. Kotlyar, L. O’Faolain, A. B. Krysa, and T. F. Krauss, “Electrically tunable multiquantum-well InGaAsP-InGaAsP microphotonic filter,” IEEE Photon. Technol. Lett. 17(4), 837–839 (2005). [CrossRef]

]. Thus, the wavelength tuning of our photodetector is mainly decided by the thermal-optic effect. When tuning power was increased, the dropping central wavelength shifted to longer wavelength.

The tunable spectral responses of one photodetector in the WSPD array were plotted in Fig. 9 . The wavelength tuning ranges of 2.9, 7.0, and 10.0nm (1538–1548nm) were achieved with the applied tuning powers of 0.2, 0.5, and 0.7W, respectively. At the tuning power of 0.7W, a 10nm wavelength shift was obtained. The tuning power efficiency was about 14.2nm/W. The dropped wavelength shift dependence on tuning power was found to be linear, as shown in Fig. 10 . The spectral linewidth less than 0.5nm were obtained simultaneously.

Fig. 9 Measured spectral responses of one photodetector in the WSPD array. The applied tuning powers are 0W, 0.2W, 0.4W, 0.5W, 0.65W and 0.7W.

Fig. 10 Peak response wavelength against applied tuning power.

The room temperature current-voltage characteristic of the device was measured without illumination. As shown in Fig. 11 , the dark current slowly increases from 2nA at 0V reverse bias to 20nA at 6V. At larger reverse biases, the dark current increases more rapidly due to tunneling at a higher electric field. The dark current is 10nA at a reverse bias of 3V. There are several sources contributing to the dark current, including the imperfect surface passivation [22

K. Kato, “Ultrawide-band/high-frequency photodetectors,” IEEE Trans. Microw. Theory Tech. 47(7), 1265–1281 (1999). [CrossRef]

], diffusion current, generation recombination current, and tunneling current at high bias voltages [23

W. A. Wohlmuth, J. W. Seo, P. Fay, C. Caneau, and I. Adesida, “A high speed ITO-InAlAs-InGaAs Schottky-barrier photodetector,” IEEE Photon. Technol. Lett. 9(10), 1388–1390 (1997). [CrossRef]

]. The generation recombination current is mainly caused by the background dopant and the mismatch dislocations [24

J. H. Jang, G. Cueva, D. C. Dumka, W. E. Hoke, P. J. Lemonias, and I. Adesida, “Long-wavelength In_0.53Ga_0.47As metamorphic p-i-n photodiodes on GaAs substrates,” IEEE Photon. Technol. Lett. 13(2), 151–153 (2001). [CrossRef]

]. The high quality heteroepitaxy growth, by using a thin low temperature buffer layer, reduces the generation recombination current due to lower mismatch dislocations.

Fig. 11 Measured dark current against reverse bias of one photodetector in the WSPD array. The dark current is 10nA at a reverse bias of 3V.

Measurement of the bandwidth was made with a tunable laser and a HP8703A lightwave component analyzer in the frequency range from 130MHz to 20GHz at 1550nm wavelength. The device was contacted by a microwave probe of 50Ω characteristic impedance and biased through an internal bias tee. The measured frequency response is shown in Fig. 12 , where the 3dB bandwidth of the device is 9.2GHz with a reverse bias of 3.0V. In our device, the bandwidth is mainly limited by the resistance-capacity (RC) time constant. In the future, smaller area photodetectors or uni-traveling carrier (UTC) structures should be fabricated to increase the response speed [25

H. Pan, Z. Li, A. Beling, and J. C. Campbell, “Measurement and modeling of high-linearity modified uni-traveling carrier photodiode with highly-doped absorber,” Opt. Express 17(22), 20221–20226 (2009), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-17-22-20221. [CrossRef] [PubMed]

–27

J. Kim, S. Kanakaraju, W. B. Johnson, and C. H. Lee, “Uni-Traveling Carrier Phototransistor,” in Conference on Lasers and Electro-Optics/International Quantum Electronics Conference, OSA Technical Digest (CD) (Optical Society of America, 2009), paper CMQQ1, http://www.opticsinfobase.org/abstract.cfm?URI=CLEO-2009-CMQQ1.

Fig. 12 Relative frequency response of one photodetector in the WSPD array. The 3dB bandwidth of the device is 9.2GHz with a reverse bias of 3.0V and an optical input power of 1μW at 1550nm wavelength.

4. Conclusion

The feasibility of a reconfigurable multi-channel WDM drop module using a WSPD array with a multistep FPC has been shown and the performance of the device has been characterized. The four-channel drop function was realized, and the dropped central wavelengths were 1538, 1550, 1559, and 1570nm. At the tuning power of 0.7W, a 10nm wavelength shift was obtained with a tuning power efficiency of 14.2nm/W. A spectral linewidth less than 0.5nm (FWHM), a 3dB bandwidth of 9.2GHz, and the peak quantum efficiencies from 13% to 20% were simultaneously obtained, in agreement with the theoretical simulation. As the key part of ROADMs, the WSPD array with the multistep FPC can increase integrated level and reduce cost, and has great potential for future low cost WDM networks.

Acknowledgments

This work was supported by National Basic Research Program of China (2010CB327601), National High Technology R&D Program of China (2007AA03Z418), 111 Project of China (B07005), Changjiang Scholars and Innovative Research Team in University of China (IRT0609), and Program of Key International Science and Technology Cooperation Projects (2006DFB11110).

References and links

1.	B. Pezeshki, F. K. Tong, J. A. Kash, D. W. Kisker, and R. M. Potemski, “Tapered Fabry-Pérot waveguide optical demultiplexer,” IEEE Photon. Technol. Lett. 5(9), 1082–1085 (1993). [CrossRef]
2.	B. Pezeshki, F. F. Tong, J. A. Kash, and D. W. Kisker, “Vertical cavity devices as wavelength selective waveguides,” J. Lightwave Technol. 12(10), 1791–1801 (1994). [CrossRef]
3.	K. Takahashi, Y. Kanamori, Y. Kokubun, and K. Hane, “A wavelength-selective add-drop switch using silicon microring resonator with a submicron-comb electrostatic actuator,” Opt. Express 16(19), 14421–14428 (2008), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-16-19-14421. [CrossRef] [PubMed]
4.	E. J. Klein, D. H. Geuzebroek, H. Kelderman, N. Gabriel Sengo, Baker, and A. Driessen, “Reconfigurable optical add-drop multiplexer using microring resonators,” IEEE Photon. Technol. Lett. 17(11), 2358–2360 (2005). [CrossRef]
5.	J. Takayesu, M. Hochberg, T. Baehr-Jones, E. Chan, P. Guangxi Wang, Sullivan, J. Yi Liao, L. Davies, A. Dalton, Scherer, and W. Krug, “A Hybrid Electrooptic Microring Resonator-Based $1 \times 4\times 1$ ROADM for Wafer Scale Optical Interconnects,” J. Lightwave Technol. 27(4), 440–448 (2009). [CrossRef]
6.	K. T. Shiu, S. S. Agashe, and S. R. Forrest, “An InP-based monolithically integrated reconfigurable optical add-drop multiplexer,” IEEE Photon. Technol. Lett. 19(19), 1445–1447 (2007). [CrossRef]
7.	C. G. M. Vreeburg, T. Uitterdijk, Y. S. Oei, M. K. Smit, F. H. Groen, E. G. Metaal, P. Demeester, and H. J. Frankena, “First InP-based reconfigurable integrated add-drop multiplexer,” IEEE Photon. Technol. Lett. 9(2), 188–190 (1997). [CrossRef]
8.	H. Huang, X. Ren, J. Lv, Q. Wang, H. Song, S. Cai, Y. Huang, and B. Qu, “Crack-free GaAs epitaxy on Si by using midpatterned growth: Application to Si-based wavelength-selective photodetector,” J. Appl. Phys. 104(11), 113114 (2008). [CrossRef]
9.	J. Lv, H. Huang, X. Ren, A. Miao, Y. Li, H. Song, Q. Wang, Y. Huang, and S. Cai, “Monolithically integrated long-wavelength tunable photodetector,” J. Lightwave Technol. 26(3), 338–342 (2008). [CrossRef]
10.	X. Duan, Y. Huang, H. Huang, X. Ren, Q. Wang, Y. Shang, X. Ye, and S. Cai, “Monolithically integrated photodetector array with a multistep cavity for multiwavelength receiving applications,” J. Lightwave Technol. 27(21), 4697–4702 (2009). [CrossRef]
11.	I. Christiaens, G. Roelkens, K. D. Mesel, D. V. Thourhout, and R. Baets, “Thin-Film Devices Fabricated With Benzocyclobutene Adhesive Wafer Bonding,” J. Lightwave Technol. 23(2), 517–523 (2005). [CrossRef]
12.	V. Passaro, F. Magno, and A. Tsarev, “Investigation of thermo-optic effect and multi-reflector tunable filter/multiplexer in SOI waveguides,” Opt. Express 13(9), 3429–3437 (2005), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-13-9-3429. [CrossRef] [PubMed]
13.	T. Chu, H. Yamada, A. Gomyo, A. Ushida, S. Ishida, and Y. Arakawa, “Integrated Reconfigurable Optical Add-Drop Multiplexer (R-OADM) based on Silicon Nano-Photonic Waveguides,” in Proceedings of the 3rd IEEE International Conference on Group IV Photonics, 261–263 (2006).
14.	H. Halbritter, F. Riemenschneider, S. Syguda, C. Dhanavantri, M. Strassner, A. Tarraf, B. R. Singh, I. Sagnes, and P. Meissner, “Tunable and wavelength selective pin photodiode,” Electron. Lett. 40(6), 388–390 (2004). [CrossRef]
15.	M. S. Ünlü and S. Strite, “Resonant cavity enhanced photonic devices,” Appl. Phys. (Berl.) 78, 607–639 (1995). [CrossRef]
16.	I. Kimukin, N. Biyikli, and E. Ozbay, “High-performance 1.55 micron resonant cavity enhanced photodetector,” in Optical Fiber Communications Conference, A. Sawchuk, ed., Vol. 70 of OSA Trends in Optics and Photonics (Optical Society of America, 2002), paper TuW6, http://www.opticsinfobase.org/abstract.cfm?URI=OFC-2002-TuW6.
17.	A. Beling and J. C. Campbell, “InP-Based High-Speed Photodetectors,” J. Lightwave Technol. 27(3), 343–355 (2009). [CrossRef]
18.	L. Domash, M. Wu, N. Nemchuk, and E. Ma, “Tunable and switchable Multiple-Cavity Thin Film Filters,” J. Lightwave Technol. 22(1), 126–135 (2004). [CrossRef]
19.	H. Huang, X. Ren, X. Wang, H. Cui, W. Wang, A. Miao, Y. Li, Q. Wang, and Y. Huang, “Theory and experiments of a tunable wavelength-selective photodetector based on a taper cavity,” Appl. Opt. 45(33), 8448–8453 (2006), http://www.opticsinfobase.org/ao/abstract.cfm?URI=ao-45-33-8448. [CrossRef] [PubMed]
20.	A. Spisser, R. Ledantec, C. Seassal, J. L. Leclercq, T. Benyattou, D. Rondi, R. Blondeau, G. Guillot, and P. Viktorovitch, “Highly selective and widely tunable 1.55-μm InP/air-gap micromachined Fabry-Perot filter for optical communications,” IEEE Photon. Technol. Lett. 10(9), 1259–1261 (1998). [CrossRef]
21.	M. V. Kotlyar, L. O’Faolain, A. B. Krysa, and T. F. Krauss, “Electrically tunable multiquantum-well InGaAsP-InGaAsP microphotonic filter,” IEEE Photon. Technol. Lett. 17(4), 837–839 (2005). [CrossRef]
22.	K. Kato, “Ultrawide-band/high-frequency photodetectors,” IEEE Trans. Microw. Theory Tech. 47(7), 1265–1281 (1999). [CrossRef]
23.	W. A. Wohlmuth, J. W. Seo, P. Fay, C. Caneau, and I. Adesida, “A high speed ITO-InAlAs-InGaAs Schottky-barrier photodetector,” IEEE Photon. Technol. Lett. 9(10), 1388–1390 (1997). [CrossRef]
24.	J. H. Jang, G. Cueva, D. C. Dumka, W. E. Hoke, P. J. Lemonias, and I. Adesida, “Long-wavelength In_0.53Ga_0.47As metamorphic p-i-n photodiodes on GaAs substrates,” IEEE Photon. Technol. Lett. 13(2), 151–153 (2001). [CrossRef]
25.	H. Pan, Z. Li, A. Beling, and J. C. Campbell, “Measurement and modeling of high-linearity modified uni-traveling carrier photodiode with highly-doped absorber,” Opt. Express 17(22), 20221–20226 (2009), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-17-22-20221. [CrossRef] [PubMed]
26.	A. Wakatsuki, T. Furuta, Y. Muramoto, and T. Ishibashi, “High-Speed Photodiode and Optical Receiver Technologies,” in Optical Fiber Communication Conference, OSA Technical Digest (CD) (Optical Society of America, 2009), paper OMK1, http://www.opticsinfobase.org/abstract.cfm?URI=OFC-2009-OMK1.
27.	J. Kim, S. Kanakaraju, W. B. Johnson, and C. H. Lee, “Uni-Traveling Carrier Phototransistor,” in Conference on Lasers and Electro-Optics/International Quantum Electronics Conference, OSA Technical Digest (CD) (Optical Society of America, 2009), paper CMQQ1, http://www.opticsinfobase.org/abstract.cfm?URI=CLEO-2009-CMQQ1.

OCIS Codes
(040.1240) Detectors : Arrays
(060.4230) Fiber optics and optical communications : Multiplexing
(060.4510) Fiber optics and optical communications : Optical communications
(230.3120) Optical devices : Integrated optics devices
(230.5160) Optical devices : Photodetectors

ToC Category:
Fiber Optics and Optical Communications

History
Original Manuscript: January 19, 2010
Revised Manuscript: February 24, 2010
Manuscript Accepted: February 24, 2010
Published: March 9, 2010

Citation
Xiaofeng Duan, Yongqing Huang, Xiaomin Ren, Hui Huang, Sanxian Xie, Qi Wang, and Shiwei Cai, "Reconfigurable multi-channel WDM drop module using a tunable wavelength-selective photodetector array," Opt. Express 18, 5879-5889 (2010)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-18-6-5879

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References

B. Pezeshki, F. K. Tong, J. A. Kash, D. W. Kisker, and R. M. Potemski, “Tapered Fabry-Pérot waveguide optical demultiplexer,” IEEE Photon. Technol. Lett. 5(9), 1082–1085 (1993). [CrossRef]
B. Pezeshki, F. F. Tong, J. A. Kash, and D. W. Kisker, “Vertical cavity devices as wavelength selective waveguides,” J. Lightwave Technol. 12(10), 1791–1801 (1994). [CrossRef]
K. Takahashi, Y. Kanamori, Y. Kokubun, and K. Hane, “A wavelength-selective add-drop switch using silicon microring resonator with a submicron-comb electrostatic actuator,” Opt. Express 16(19), 14421–14428 (2008), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-16-19-14421 . [CrossRef] [PubMed]
E. J. Klein, D. H. Geuzebroek, H. Kelderman, N. Gabriel Sengo, Baker, and A. Driessen, “Reconfigurable optical add-drop multiplexer using microring resonators,” IEEE Photon. Technol. Lett. 17(11), 2358–2360 (2005). [CrossRef]
J. Takayesu, M. Hochberg, T. Baehr-Jones, E. Chan, P. Guangxi Wang, Sullivan, J. Yi Liao, L. Davies, A. Dalton, Scherer, and W. Krug, “A Hybrid Electrooptic Microring Resonator-Based $1 \times 4\times 1$ ROADM for Wafer Scale Optical Interconnects,” J. Lightwave Technol. 27(4), 440–448 (2009). [CrossRef]
K. T. Shiu, S. S. Agashe, and S. R. Forrest, “An InP-based monolithically integrated reconfigurable optical add-drop multiplexer,” IEEE Photon. Technol. Lett. 19(19), 1445–1447 (2007). [CrossRef]
C. G. M. Vreeburg, T. Uitterdijk, Y. S. Oei, M. K. Smit, F. H. Groen, E. G. Metaal, P. Demeester, and H. J. Frankena, “First InP-based reconfigurable integrated add-drop multiplexer,” IEEE Photon. Technol. Lett. 9(2), 188–190 (1997). [CrossRef]
H. Huang, X. Ren, J. Lv, Q. Wang, H. Song, S. Cai, Y. Huang, and B. Qu, “Crack-free GaAs epitaxy on Si by using midpatterned growth: Application to Si-based wavelength-selective photodetector,” J. Appl. Phys. 104(11), 113114 (2008). [CrossRef]
J. Lv, H. Huang, X. Ren, A. Miao, Y. Li, H. Song, Q. Wang, Y. Huang, and S. Cai, “Monolithically integrated long-wavelength tunable photodetector,” J. Lightwave Technol. 26(3), 338–342 (2008). [CrossRef]
X. Duan, Y. Huang, H. Huang, X. Ren, Q. Wang, Y. Shang, X. Ye, and S. Cai, “Monolithically integrated photodetector array with a multistep cavity for multiwavelength receiving applications,” J. Lightwave Technol. 27(21), 4697–4702 (2009). [CrossRef]
I. Christiaens, G. Roelkens, K. D. Mesel, D. V. Thourhout, and R. Baets, “Thin-Film Devices Fabricated With Benzocyclobutene Adhesive Wafer Bonding,” J. Lightwave Technol. 23(2), 517–523 (2005). [CrossRef]
V. Passaro, F. Magno, and A. Tsarev, “Investigation of thermo-optic effect and multi-reflector tunable filter/multiplexer in SOI waveguides,” Opt. Express 13(9), 3429–3437 (2005), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-13-9-3429 . [CrossRef] [PubMed]
T. Chu, H. Yamada, A. Gomyo, A. Ushida, S. Ishida, and Y. Arakawa, “Integrated Reconfigurable Optical Add-Drop Multiplexer (R-OADM) based on Silicon Nano-Photonic Waveguides,” in Proceedings of the 3rd IEEE International Conference on Group IV Photonics, 261–263 (2006).
H. Halbritter, F. Riemenschneider, S. Syguda, C. Dhanavantri, M. Strassner, A. Tarraf, B. R. Singh, I. Sagnes, and P. Meissner, “Tunable and wavelength selective pin photodiode,” Electron. Lett. 40(6), 388–390 (2004). [CrossRef]
M. S. Ünlü and S. Strite, “Resonant cavity enhanced photonic devices,” Appl. Phys. (Berl.) 78, 607–639 (1995). [CrossRef]
I. Kimukin, N. Biyikli, and E. Ozbay, “High-performance 1.55 micron resonant cavity enhanced photodetector,” in Optical Fiber Communications Conference, A. Sawchuk, ed., Vol. 70 of OSA Trends in Optics and Photonics (Optical Society of America, 2002), paper TuW6, http://www.opticsinfobase.org/abstract.cfm?URI=OFC-2002-TuW6 .
A. Beling and J. C. Campbell, “InP-Based High-Speed Photodetectors,” J. Lightwave Technol. 27(3), 343–355 (2009). [CrossRef]
L. Domash, M. Wu, N. Nemchuk, and E. Ma, “Tunable and switchable Multiple-Cavity Thin Film Filters,” J. Lightwave Technol. 22(1), 126–135 (2004). [CrossRef]
H. Huang, X. Ren, X. Wang, H. Cui, W. Wang, A. Miao, Y. Li, Q. Wang, and Y. Huang, “Theory and experiments of a tunable wavelength-selective photodetector based on a taper cavity,” Appl. Opt. 45(33), 8448–8453 (2006), http://www.opticsinfobase.org/ao/abstract.cfm?URI=ao-45-33-8448 . [CrossRef] [PubMed]
A. Spisser, R. Ledantec, C. Seassal, J. L. Leclercq, T. Benyattou, D. Rondi, R. Blondeau, G. Guillot, and P. Viktorovitch, “Highly selective and widely tunable 1.55-μm InP/air-gap micromachined Fabry-Perot filter for optical communications,” IEEE Photon. Technol. Lett. 10(9), 1259–1261 (1998). [CrossRef]
M. V. Kotlyar, L. O’Faolain, A. B. Krysa, and T. F. Krauss, “Electrically tunable multiquantum-well InGaAsP-InGaAsP microphotonic filter,” IEEE Photon. Technol. Lett. 17(4), 837–839 (2005). [CrossRef]
K. Kato, “Ultrawide-band/high-frequency photodetectors,” IEEE Trans. Microw. Theory Tech. 47(7), 1265–1281 (1999). [CrossRef]
W. A. Wohlmuth, J. W. Seo, P. Fay, C. Caneau, and I. Adesida, “A high speed ITO-InAlAs-InGaAs Schottky-barrier photodetector,” IEEE Photon. Technol. Lett. 9(10), 1388–1390 (1997). [CrossRef]
J. H. Jang, G. Cueva, D. C. Dumka, W. E. Hoke, P. J. Lemonias, and I. Adesida, “Long-wavelength In0.53Ga0.47As metamorphic p-i-n photodiodes on GaAs substrates,” IEEE Photon. Technol. Lett. 13(2), 151–153 (2001). [CrossRef]
H. Pan, Z. Li, A. Beling, and J. C. Campbell, “Measurement and modeling of high-linearity modified uni-traveling carrier photodiode with highly-doped absorber,” Opt. Express 17(22), 20221–20226 (2009), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-17-22-20221 . [CrossRef] [PubMed]
A. Wakatsuki, T. Furuta, Y. Muramoto, and T. Ishibashi, “High-Speed Photodiode and Optical Receiver Technologies,” in Optical Fiber Communication Conference, OSA Technical Digest (CD) (Optical Society of America, 2009), paper OMK1, http://www.opticsinfobase.org/abstract.cfm?URI=OFC-2009-OMK1 .
J. Kim, S. Kanakaraju, W. B. Johnson, and C. H. Lee, “Uni-Traveling Carrier Phototransistor,” in Conference on Lasers and Electro-Optics/International Quantum Electronics Conference, OSA Technical Digest (CD) (Optical Society of America, 2009), paper CMQQ1, http://www.opticsinfobase.org/abstract.cfm?URI=CLEO-2009-CMQQ1 .

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