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Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 22, Iss. 4 — Feb. 24, 2014
  • pp: 4692–4698
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Ultra-compact 32-channel drop filter with 100 GHz spacing

Yasushi Takahashi, Takashi Asano, Daiki Yamashita, and Susumu Noda  »View Author Affiliations


Optics Express, Vol. 22, Issue 4, pp. 4692-4698 (2014)
http://dx.doi.org/10.1364/OE.22.004692


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Abstract

We demonstrated 32-channel drop filters with 100 GHz spacing consisting of arrayed nanocavities and a waveguide in a photonic crystal silicon slab. Changing the lattice constant of the nanocavities on the subnanometer scale successfully controlled the drop wavelengths at 100 GHz spacing in the wavelength range between 1510 and 1550 nm. The device size was as small as 15 μm × 270 μm, and the variation in drop wavelengths was less than 0.3 nm in terms of standard deviation. We also present a movie showing the operation of the drop filter, demonstrating that the arrayed nanocavities have the potential for developing ultracompact 100 GHz spaced filters in a dense wavelength division multiplexing system.

© 2014 Optical Society of America

1. Introduction

Two-dimensional (2D) photonic crystal (PC) slabs constructed from silicon-on-insulator (SOI) wafers have been used to realize ultrahigh-Q nanocavities [1

1. Y. Akahane, T. Asano, B. S. Song, and S. Noda, “High-Q photonic nanocavity in a two-dimensional photonic crystal,” Nature 425(6961), 944–947 (2003). [CrossRef] [PubMed]

4

4. H. Sekoguchi, Y. Takahashi, T. Asano, and S. Noda, “Photonic crystal nanocavity with a Q-factor of ~9 million,” Opt. Express 22(1), 916–924 (2014). [CrossRef] [PubMed]

] and a very low-loss waveguide [5

5. E. Kuramochi, M. Notomi, S. Hughes, A. Shinya, T. Watanabe, and L. Ramunno, “Disorder-induced scattering loss of line-defect waveguides in photonic crystal slabs,” Phys. Rev. B 72(16), 161318 (2005). [CrossRef]

] due to well-developed nanofabrication techniques. Coupled nanocavity-waveguide systems in silicon (Si) slabs have been used to realize various functional devices with ultra-small sizes, such as photodetectors [6

6. T. Tanabe, H. Sumikura, H. Taniyama, A. Shinya, and M. Notomi, “All-silicon sub-Gb/s telecom detector with low dark current and high quantum efficiency on chip,” Appl. Phys. Lett. 96(10), 101103 (2010). [CrossRef]

,7

7. L. D. Haret, X. Checoury, Z. Han, P. Boucaud, S. Combrié, and A. De Rossi, “All-silicon photonic crystal photoconductor on silicon-on-insulator at telecom wavelength,” Opt. Express 18(23), 23965–23972 (2010). [CrossRef] [PubMed]

], modulators [8

8. T. Tanabe, K. Nishiguchi, E. Kuramochi, and M. Notomi, “Low power and fast electro-optic silicon modulator with lateral p-i-n embedded photonic crystal nanocavity,” Opt. Express 17(25), 22505–22513 (2009). [CrossRef] [PubMed]

,9

9. K. Debnath, L. O’Faolain, F. Y. Gardes, A. G. Steffan, G. T. Reed, and T. F. Krauss, “Cascaded modulator architecture for WDM applications,” Opt. Express 20(25), 27420–27428 (2012). [CrossRef] [PubMed]

], and a Raman laser [10

10. Y. Takahashi, Y. Inui, M. Chihara, T. Asano, R. Terawaki, and S. Noda, “A micrometre-scale Raman silicon laser with a microwatt threshold,” Nature 498(7455), 470–474 (2013). [CrossRef] [PubMed]

]. These devices should have good compatibility with complementary metal oxide semiconductor technology [11

11. M. Shinkawa, N. Ishikura, Y. Hama, K. Suzuki, and T. Baba, “Nonlinear enhancement in photonic crystal slow light waveguides fabricated using CMOS-compatible process,” Opt. Express 19(22), 22208–22218 (2011). [CrossRef] [PubMed]

,12

12. H. C. Nguyen, N. Yazawa, S. Hashimoto, S. Otsuka, and T. Baba, “Sub-100 μm Photonic Crystal Si Optical Modulators: Spectral, Athermal, and High-Speed Performance,” IEEE J. Sel. Top. Quantum Electron. 19(6), 127 (2013). [CrossRef]

], and thus Si PC slabs are a promising platform for large-scale-integration photonic chips.

Wavelength-selective filters consisting of nanocavities and waveguides in Si slabs have an ultrasmall footprint for a single port, less than 10 μm × 10 μm, and therefore, they have been intensively studied [13

13. S. Fan, P. R. Villeneuve, and J. D. Joannopoulos, “Channel drop tunneling through localized states,” Phys. Rev. Lett. 80(5), 960–963 (1998). [CrossRef]

16

16. B. S. Song, S. Noda, and T. Asano, “Photonic devices based on in-plane hetero photonic crystals,” Science 300(5625), 1537 (2003). [CrossRef] [PubMed]

]. In 2003, it was demonstrated that a nanocavity with three aligned missing air holes (L3 cavity) has good properties in terms of filtering resolution, radiation pattern, and broad free spectral range (FSR) [17

17. Y. Akahane, T. Asano, B.-S. Song, and S. Noda, “Investigation of high-Q channel drop filters using donor-type defects in two-dimensional photonic crystal slabs,” Appl. Phys. Lett. 83(8), 1512–1514 (2003). [CrossRef]

]. Subsequently, a flat-top response using two cascaded nanocavities [18

18. Y. Akahane, T. Asano, H. Takano, B. S. Song, Y. Takana, and S. Noda, “Two-dimensional photonic-crystal-slab channeldrop filter with flat-top response,” Opt. Express 13(7), 2512–2530 (2005). [CrossRef] [PubMed]

] and a highly efficient in-plane 4-channel filter with 20 nm channel spacing [19

19. H. Takano, B. S. Song, T. Asano, and S. Noda, “Highly efficient multi-channel drop filter in a two-dimensional hetero photonic crystal,” Opt. Express 14(8), 3491–3496 (2006). [CrossRef] [PubMed]

,20

20. A. Shinya, S. Mitsugi, E. Kuramochi, and M. Notomi, “Ultrasmall multi-port channel drop filter in two-dimensional photonic crystal on silicon-on-insulator substrate,” Opt. Express 14(25), 12394–12400 (2006). [CrossRef] [PubMed]

] were demonstrated. In 2008, a 16 channel drop filter with 5 nm spacing operating in a wide range from 1510 nm to 1590 nm, where a wavelength variation with a standard deviation of ~1 nm was reported [21

21. B. S. Song, T. Nagashima, T. Asano, and S. Noda, “Resonant-wavelength control of nanocavities by nanometer-scaled adjustment of two-dimensional photonic crystal slab structures,” IEEE Photon. Technol. Lett. 20(7), 532–534 (2008). [CrossRef]

]. These studies show that PC drop filters have the potential for course wavelength division multiplexing (WDM) applications. However, they have not presented the maximum potential of the PC filters in view of the channel number, wavelength variation, and channel spacing. In particular, a filtering operation with 100 GHz (~0.8 nm) spacing, which is a landmark value in dense WDM, have not been reported yet.

Here, we report 100 GHz-spaced drop filters using 32 arrayed high-Q nanocavities. By increasing the lattice constant of the PC only in the x-direction by 0.375 nm, we successfully controlled the drop wavelengths at ~100 GHz spacing in the c-band. The variation of the operating wavelengths showed a standard deviation less than 0.30 nm. The size of a single channel unit was 15 μm × 6.5 μm, and the total device size was 15 μm × 270 μm, which is 50-times smaller than that of a Si arrayed waveguide grating (AWG) [22

22. Q. Fang, T. Y. Liow, J. F. Song, K. W. Ang, M. B. Yu, G. Q. Lo, and D. L. Kwong, “WDM multi-channel silicon photonic receiver with 320 Gbps data transmission capability,” Opt. Express 18(5), 5106–5113 (2010). [CrossRef] [PubMed]

] or filters using Si ring resonators [23

23. Q. Fang, Y. T. Phang, C. W. Tan, T. Y. Liow, M. B. Yu, G. Q. Lo, and D. L. Kwong, “Multi-channel silicon photonic receiver based on ring-resonators,” Opt. Express 18(13), 13510–13515 (2010). [CrossRef] [PubMed]

,24

24. S. Park, K. J. Kim, I. G. Kim, and G. Kim, “Si micro-ring MUX/DeMUX WDM filters,” Opt. Express 19(14), 13531–13539 (2011). [CrossRef] [PubMed]

]. A movie showing the device operation demonstrated that Si PC slabs have the potential to make ultra-compact wavelength filters for dense WDM.

2. Configuration of 1 × 32 channel drop filter and experimental setup

Figure 1
Fig. 1 (Upper) Confocal laser scanning microscope image of a 32-channel drop filter which consists of 32 photonic crystal units, PC1–PC32. (Lower) SEM view of a 0.2a shifted L3 nanocavity for the unit PCn. The lattice constant an in the x-direction was {410−0.375 × (n−1)} nm. We fabricated three samples with air holes of different radii.
shows a laser scanning microscope image of 32 arrayed nanocavities fabricated in series and a scanning electron microscope (SEM) image of a nanocavity. This device consisted of 32 PC units (PC1, PC2, ····PCn, ····PC32), each of which had a line-defect transmission waveguide and a point-defect nanocavity to extract transmitted light with a specific wavelength. A single unit had 16 periods of air holes in the x-direction (~6.5 μm) and 20 periods in the y-direction (~15 μm). The length of the waveguide was 270 μm. In order to achieve 100-GHz spacing of the resonant wavelengths from the neighboring nanocavities, the lattice constants an in the x-direction were changed by 0.375 nm from 398.375 nm (PC32) to 410.000 nm (PC1): an (nm) = 410−0.375 × (n−1). On the other hand, the lattice constants in the y-direction were the same, 710 nm, for all units to maintain the structural uniformity. This method enabled fine wavelength control and could reduce the partial reflection of transmitted light at the seams of each unit. The width of the transmission waveguide was 738 nm, and the separation from the nanocavities was 6 rows of air holes in all regions. The thickness of the Si slab was 220 nm.

Figure 2
Fig. 2 Measurement setup used to investigate the drop wavelengths of arrayed nanocavities. Pol: polarizer. OL: objective lens. BS: beam splitter. M: mirror on a flip mount stage. PD: InGaAs photodiode. NIR camera: near-infrared InGaAs camera.
shows the measurement setup used to investigate the spectral properties of the 32 nanocavities. The light from a tunable cw laser was split into two beams. One beam was sent to a high-resolution wavelength meter. The other was modulated by a mechanical chopper at a frequency of ~1 kHz with a 50% duty ratio and was focused by a 0.40-numerical-aperture (N.A.) objective lens on the facet of the excitation waveguide with TE polarization. When the incident wavelength matched the resonant wavelengths of the nanocavities, the transmitted light was extracted in the direction perpendicular to the slab, as shown in Fig. 1. The dropped light was collected by a 0.65-N.A. objective lens ( × 50). The sample was placed on a high-precision 6-axis stage, and the positions of the optical components were adjusted using near-infrared (NIR) cameras such that only the dropped light from a single cavity was injected into the InGaAs photodiode. The intensity of the dropped light was measured by a lock-in amplifier system as a function of the laser wavelength.

3. Experimental results and discussion

Figure 4
Fig. 4 Near-infrared camera shots of the 32-channel drop filter with r = 110 nm when the wavelength of the transmitted laser was scanned from 1525 to 1545 nm at a speed of 2 nm per second (Media 1). A movie showing the operation of the drop filter consisting of 0.15a shifted L3 cavities is presented in Media 2. Movies were obtained with exposure time of 10 millisecond, 25 frames per second, and camera resolution of 320 × 256 pixels.
(Media 1) shows near-infrared camera images for the drop filter with r = 110 nm when the transmitted laser wavelength was scanned from 1525 to 1545 nm. The sample was located in air and was illuminated by the lamp. The dropped spots in Figs. 4(a)-4(c) represent emission from the cavities for PC30, PC23, and PC15, respectively. All cavities clearly emitted light with the same pattern. Although the dropped spots have the side lobes in 0.2an shifted L3 cavity, single-lobed spot can be obtained in the 0.15an shifted L3 cavity as presented in Media 2 (the cavities have the same structural parameters as those in Fig. 1). The movies clearly demonstrate that the transmitted laser light was extracted from the nanocavities in succession, and that two different cavities rarely emit simultaneously. These results clearly show that the device shown in Fig. 1 has the potential to be used in 100 GHz spaced filters.

It is important to briefly refer to recent results for other types of drop filters in Si photonics. A 16-channel silica AWG with 200 GHz spacing having dimensions of 4.0 mm × 2.7 mm on a Si chip has been reported [27

27. H. Nishi, T. Tsuchizawa, R. Kou, H. Shinojima, T. Yamada, H. Kimura, Y. Ishikawa, K. Wada, and K. Yamada, “Monolithic integration of a silica AWG and Ge photodiodes on Si photonic platform for one-chip WDM receiver,” Opt. Express 20(8), 9312–9321 (2012). [CrossRef] [PubMed]

]. A 32-channel Si AWG with 200 GHz spacing with a smaller size of 400 μm × 500 μm, owing to the high refractive index of Si, has also been demonstrated [22

22. Q. Fang, T. Y. Liow, J. F. Song, K. W. Ang, M. B. Yu, G. Q. Lo, and D. L. Kwong, “WDM multi-channel silicon photonic receiver with 320 Gbps data transmission capability,” Opt. Express 18(5), 5106–5113 (2010). [CrossRef] [PubMed]

]. This size may be comparable to filters using Si ring resonators when the channel number is 32 [23

23. Q. Fang, Y. T. Phang, C. W. Tan, T. Y. Liow, M. B. Yu, G. Q. Lo, and D. L. Kwong, “Multi-channel silicon photonic receiver based on ring-resonators,” Opt. Express 18(13), 13510–13515 (2010). [CrossRef] [PubMed]

,24

24. S. Park, K. J. Kim, I. G. Kim, and G. Kim, “Si micro-ring MUX/DeMUX WDM filters,” Opt. Express 19(14), 13531–13539 (2011). [CrossRef] [PubMed]

]. Our 32-channel drop filter with 100 GHz spacing had dimensions of 15 μm × 270 μm, which is 50-times smaller than the Si AWG. It is noted that the operating wavelengths can be thermally tuned all together, where the small device size will be advantageous. Furthermore, shifted L3 cavities with a broad FSR of more than 60 nm are attractive for multichannel operation.

Figure 5(a)
Fig. 5 (a) Normalized drop spectra for 32 nanocavities in the sample with r = 110 nm. (b) Histogram of the Qexp values for 32 channels. (c) Histogram of the drop efficiencies.
shows the drop spectra for 32 channels in the sample with r = 110 nm, where each spectrum is normalized independently. Figure 5(b) shows the histogram of the experimental Q values (Qexp) for 32 cavities, which are estimated from the linewidths and the peak wavelengths for the drop spectra. The values randomly vary centered at 4.7 × 104 ranging between 2.4 × 104 and 7.3 × 104. The Qexp is determined by three Q factors,
1Qexp=1Qdes+1Qin+1Qimp.
(1)
The Qdes is the design value calculated by 3D FDTD and the Qin is determined by the optical coupling with the transmission waveguide. The Qimp is the additional loss factor due to the structural imperfections [28

28. T. Asano, B. S. Song, and S. Noda, “Analysis of the experimental Q factors (~ 1 million) of photonic crystal nanocavities,” Opt. Express 14(5), 1996–2002 (2006). [CrossRef] [PubMed]

,29

29. H. Hagino, Y. Takahashi, Y. Tanaka, T. Asano, and S. Noda, “Effects of fluctuation in air hole radii and positions on optical characteristics in photonic crystal heterostructure nanocavities,” Phys. Rev. B 79(8), 085112 (2009). [CrossRef]

], which is negligible in this sample since it is much larger than Qdes and Qin values [3

3. Y. Taguchi, Y. Takahashi, Y. Sato, T. Asano, and S. Noda, “Statistical studies of photonic heterostructure nanocavities with an average Q factor of three million,” Opt. Express 19(12), 11916–11921 (2011). [CrossRef] [PubMed]

,4

4. H. Sekoguchi, Y. Takahashi, T. Asano, and S. Noda, “Photonic crystal nanocavity with a Q-factor of ~9 million,” Opt. Express 22(1), 916–924 (2014). [CrossRef] [PubMed]

]. Therefore, the variation of Qexp is mainly caused by the fluctuation in Qin. The drop efficiency (ηdrop) can be evaluated from the following relation in the device configuration shown in Fig. 1 [15

15. A. Chutinan, M. Mochizuki, M. Imada, and S. Noda, “Surface-emitting channel drop filters using single defects in two-dimensional photonic crystal slabs,” Appl. Phys. Lett. 79(17), 2690–2692 (2001). [CrossRef]

,30

30. C. Manolatou, M. J. Khan, S. Fan, P. R. Villeneuve, H. A. Haus, and J. D. Joannopoulos, “Coupling of modes analysis of resonant channel add-drop filters,” IEEE J. Quantum Electron. 35(9), 1322–1331 (1999). [CrossRef]

]:
ηdrop=(Qin/Qdes)(1+Qin/Qdes)2.
(2)
When the Qin and Qdes are equal, the maximum efficiency of 25% is expected where radiation into the direction opposite to the objective lens is taken into account (the efficiencies more than 70% were reported in other device configurations [19

19. H. Takano, B. S. Song, T. Asano, and S. Noda, “Highly efficient multi-channel drop filter in a two-dimensional hetero photonic crystal,” Opt. Express 14(8), 3491–3496 (2006). [CrossRef] [PubMed]

,20

20. A. Shinya, S. Mitsugi, E. Kuramochi, and M. Notomi, “Ultrasmall multi-port channel drop filter in two-dimensional photonic crystal on silicon-on-insulator substrate,” Opt. Express 14(25), 12394–12400 (2006). [CrossRef] [PubMed]

]). Figure 5(c) presents the histogram of the drop efficiencies for 32 channels. The 27 channels achieved the efficiency larger than 20%. The others having the lower efficiencies are due to the smaller Qin. Changing the width of transmission waveguide will be an effective method to finely tune the Qin.

In order to further decrease the wavelength variation, the fabrication accuracy of the air holes should be enhanced, because random fluctuations of the radii and positions of the air holes may be the main cause of these variations [3

3. Y. Taguchi, Y. Takahashi, Y. Sato, T. Asano, and S. Noda, “Statistical studies of photonic heterostructure nanocavities with an average Q factor of three million,” Opt. Express 19(12), 11916–11921 (2011). [CrossRef] [PubMed]

,29

29. H. Hagino, Y. Takahashi, Y. Tanaka, T. Asano, and S. Noda, “Effects of fluctuation in air hole radii and positions on optical characteristics in photonic crystal heterostructure nanocavities,” Phys. Rev. B 79(8), 085112 (2009). [CrossRef]

]. The fluctuation in slab thickness may also have some influence. The resonant wavelength of the nanocavity for PC1 (PC32) with r = 110 nm shifts by 1.09 nm (1.54 nm) per 1 nm change in slab thickness, according to 3D FDTD calculations. The roughness average of the top surface of the fabricated samples is 0.1−0.2 nm within a micrometer-size area, as determined by atomic force microscope (AFM) measurements [25

25. R. Terawaki, Y. Takahashi, M. Chihara, Y. Inui, and S. Noda, “Ultrahigh-Q photonic crystal nanocavities in wide optical telecommunication bands,” Opt. Express 20(20), 22743–22752 (2012). [CrossRef] [PubMed]

,28

28. T. Asano, B. S. Song, and S. Noda, “Analysis of the experimental Q factors (~ 1 million) of photonic crystal nanocavities,” Opt. Express 14(5), 1996–2002 (2006). [CrossRef] [PubMed]

]. Because the volume of the nanocavity is very small, the thickness fluctuation in a micrometer area may cause a wavelength variation with a magnitude of ~0.1 nm. In order to compensate for the inevitable wavelength variation, postprocessing to tune the wavelengths may be one approach, for example, local oxidation by laser irradiation or AFM lithography [31

31. C. J. Chen, J. Zheng, T. Gu, J. F. McMillan, M. Yu, G. Q. Lo, D. L. Kwong, and C. W. Wong, “Selective tuning of high-Q silicon photonic crystal nanocavities via laser-assisted local oxidation,” Opt. Express 19(13), 12480–12489 (2011). [CrossRef] [PubMed]

,32

32. A. Yokoo, T. Tanabe, E. Kuramochi, and M. Notomi, “Ultrahigh-Q nanocavities written with a nanoprobe,” Nano Lett. 11(9), 3634–3642 (2011). [CrossRef] [PubMed]

].

For practical applications, a flat-top spectral shape will be important for increasing the 1 dB bandwidth without crosstalk to neighboring channels, though each spectrum in Fig. 5(a) has a single Lorentzian peak. This will be achieved by using coupled nanocavities with optimum Q factors [18

18. Y. Akahane, T. Asano, H. Takano, B. S. Song, Y. Takana, and S. Noda, “Two-dimensional photonic-crystal-slab channeldrop filter with flat-top response,” Opt. Express 13(7), 2512–2530 (2005). [CrossRef] [PubMed]

]. Such a demonstration will be a significant step for PC drop filters where the 1 dB bandwidth and the variation of dropped power should be investigated. The in-plane drop operation will be also important. This can be resolved by using structures like those reported in [19

19. H. Takano, B. S. Song, T. Asano, and S. Noda, “Highly efficient multi-channel drop filter in a two-dimensional hetero photonic crystal,” Opt. Express 14(8), 3491–3496 (2006). [CrossRef] [PubMed]

,20

20. A. Shinya, S. Mitsugi, E. Kuramochi, and M. Notomi, “Ultrasmall multi-port channel drop filter in two-dimensional photonic crystal on silicon-on-insulator substrate,” Opt. Express 14(25), 12394–12400 (2006). [CrossRef] [PubMed]

], where output waveguides and heterostructure interface mirrors for cooperative interference should be integrated. The increase in the device footprint caused by these structural modifications will be slight. By adding waveguided Ge-on-Si photodetectors [22

22. Q. Fang, T. Y. Liow, J. F. Song, K. W. Ang, M. B. Yu, G. Q. Lo, and D. L. Kwong, “WDM multi-channel silicon photonic receiver with 320 Gbps data transmission capability,” Opt. Express 18(5), 5106–5113 (2010). [CrossRef] [PubMed]

] or Si nanocavity detectors [6

6. T. Tanabe, H. Sumikura, H. Taniyama, A. Shinya, and M. Notomi, “All-silicon sub-Gb/s telecom detector with low dark current and high quantum efficiency on chip,” Appl. Phys. Lett. 96(10), 101103 (2010). [CrossRef]

,7

7. L. D. Haret, X. Checoury, Z. Han, P. Boucaud, S. Combrié, and A. De Rossi, “All-silicon photonic crystal photoconductor on silicon-on-insulator at telecom wavelength,” Opt. Express 18(23), 23965–23972 (2010). [CrossRef] [PubMed]

], it should be possible to construct a demultiplexing (DEMUX) receiver. Also the air-bridge structure used in this study has some demerits, including mechanical instability, low thermal conductivity, and vulnerability to contamination. This can be resolved by utilizing the low-index-glass cladding structure having sufficiently high Q values [33

33. S. W. Jeon, J. K. Han, B. S. Song, and S. Noda, “Glass-embedded two-dimensional silicon photonic crystal devices with a broad bandwidth waveguide and a high quality nanocavity,” Opt. Express 18(18), 19361–19366 (2010). [CrossRef] [PubMed]

]. By integrating a Ge PD on the glass cladding, it should be possible to make a DEMUX receiver with vertical coupling.

4. Summary

Here, we report 32-channel wavelength filters with 100 GHz spacing using arrayed nanocavities. By increasing the lattice constant only in the x-direction by 0.375 nm, we successfully controlled the drop wavelengths at ~100 GHz spacing. The variation in drop wavelength was less than 0.30 nm in a standard deviation. The total device size is as small as 15 μm × 270 μm, which is 50-times smaller than that of a Si AWG. A movie showing the device operation clearly demonstrates that the transmitted laser light is extracted from the nanocavities in succession and two different cavities rarely emit simultaneously. These results are the first demonstration that PC wavelength filters have the potential for use in dense WDM applications. This study will also contribute to the development of multichannel sensors using arrayed high-Q nanocavities.

Acknowledgment

Y. T is supported by NanoSquare program, Funds for the Development of Human Resources in Science and Technology commissioned by MEXT. This work was supported by JSPS KAKENHI (grant numbers 23686015), Future Pioneering Projects, and CPHoST program.

References and links

1.

Y. Akahane, T. Asano, B. S. Song, and S. Noda, “High-Q photonic nanocavity in a two-dimensional photonic crystal,” Nature 425(6961), 944–947 (2003). [CrossRef] [PubMed]

2.

B. S. Song, S. Noda, T. Asano, and Y. Akahane, “Ultra-High-Q photonic double-heterostructure nanocavity,” Nat. Mater. 4(3), 207–210 (2005). [CrossRef]

3.

Y. Taguchi, Y. Takahashi, Y. Sato, T. Asano, and S. Noda, “Statistical studies of photonic heterostructure nanocavities with an average Q factor of three million,” Opt. Express 19(12), 11916–11921 (2011). [CrossRef] [PubMed]

4.

H. Sekoguchi, Y. Takahashi, T. Asano, and S. Noda, “Photonic crystal nanocavity with a Q-factor of ~9 million,” Opt. Express 22(1), 916–924 (2014). [CrossRef] [PubMed]

5.

E. Kuramochi, M. Notomi, S. Hughes, A. Shinya, T. Watanabe, and L. Ramunno, “Disorder-induced scattering loss of line-defect waveguides in photonic crystal slabs,” Phys. Rev. B 72(16), 161318 (2005). [CrossRef]

6.

T. Tanabe, H. Sumikura, H. Taniyama, A. Shinya, and M. Notomi, “All-silicon sub-Gb/s telecom detector with low dark current and high quantum efficiency on chip,” Appl. Phys. Lett. 96(10), 101103 (2010). [CrossRef]

7.

L. D. Haret, X. Checoury, Z. Han, P. Boucaud, S. Combrié, and A. De Rossi, “All-silicon photonic crystal photoconductor on silicon-on-insulator at telecom wavelength,” Opt. Express 18(23), 23965–23972 (2010). [CrossRef] [PubMed]

8.

T. Tanabe, K. Nishiguchi, E. Kuramochi, and M. Notomi, “Low power and fast electro-optic silicon modulator with lateral p-i-n embedded photonic crystal nanocavity,” Opt. Express 17(25), 22505–22513 (2009). [CrossRef] [PubMed]

9.

K. Debnath, L. O’Faolain, F. Y. Gardes, A. G. Steffan, G. T. Reed, and T. F. Krauss, “Cascaded modulator architecture for WDM applications,” Opt. Express 20(25), 27420–27428 (2012). [CrossRef] [PubMed]

10.

Y. Takahashi, Y. Inui, M. Chihara, T. Asano, R. Terawaki, and S. Noda, “A micrometre-scale Raman silicon laser with a microwatt threshold,” Nature 498(7455), 470–474 (2013). [CrossRef] [PubMed]

11.

M. Shinkawa, N. Ishikura, Y. Hama, K. Suzuki, and T. Baba, “Nonlinear enhancement in photonic crystal slow light waveguides fabricated using CMOS-compatible process,” Opt. Express 19(22), 22208–22218 (2011). [CrossRef] [PubMed]

12.

H. C. Nguyen, N. Yazawa, S. Hashimoto, S. Otsuka, and T. Baba, “Sub-100 μm Photonic Crystal Si Optical Modulators: Spectral, Athermal, and High-Speed Performance,” IEEE J. Sel. Top. Quantum Electron. 19(6), 127 (2013). [CrossRef]

13.

S. Fan, P. R. Villeneuve, and J. D. Joannopoulos, “Channel drop tunneling through localized states,” Phys. Rev. Lett. 80(5), 960–963 (1998). [CrossRef]

14.

S. Noda, A. Chutinan, and M. Imada, “Trapping and emission of photons by a single defect in a photonic bandgap structure,” Nature 407(6804), 608–610 (2000). [CrossRef] [PubMed]

15.

A. Chutinan, M. Mochizuki, M. Imada, and S. Noda, “Surface-emitting channel drop filters using single defects in two-dimensional photonic crystal slabs,” Appl. Phys. Lett. 79(17), 2690–2692 (2001). [CrossRef]

16.

B. S. Song, S. Noda, and T. Asano, “Photonic devices based on in-plane hetero photonic crystals,” Science 300(5625), 1537 (2003). [CrossRef] [PubMed]

17.

Y. Akahane, T. Asano, B.-S. Song, and S. Noda, “Investigation of high-Q channel drop filters using donor-type defects in two-dimensional photonic crystal slabs,” Appl. Phys. Lett. 83(8), 1512–1514 (2003). [CrossRef]

18.

Y. Akahane, T. Asano, H. Takano, B. S. Song, Y. Takana, and S. Noda, “Two-dimensional photonic-crystal-slab channeldrop filter with flat-top response,” Opt. Express 13(7), 2512–2530 (2005). [CrossRef] [PubMed]

19.

H. Takano, B. S. Song, T. Asano, and S. Noda, “Highly efficient multi-channel drop filter in a two-dimensional hetero photonic crystal,” Opt. Express 14(8), 3491–3496 (2006). [CrossRef] [PubMed]

20.

A. Shinya, S. Mitsugi, E. Kuramochi, and M. Notomi, “Ultrasmall multi-port channel drop filter in two-dimensional photonic crystal on silicon-on-insulator substrate,” Opt. Express 14(25), 12394–12400 (2006). [CrossRef] [PubMed]

21.

B. S. Song, T. Nagashima, T. Asano, and S. Noda, “Resonant-wavelength control of nanocavities by nanometer-scaled adjustment of two-dimensional photonic crystal slab structures,” IEEE Photon. Technol. Lett. 20(7), 532–534 (2008). [CrossRef]

22.

Q. Fang, T. Y. Liow, J. F. Song, K. W. Ang, M. B. Yu, G. Q. Lo, and D. L. Kwong, “WDM multi-channel silicon photonic receiver with 320 Gbps data transmission capability,” Opt. Express 18(5), 5106–5113 (2010). [CrossRef] [PubMed]

23.

Q. Fang, Y. T. Phang, C. W. Tan, T. Y. Liow, M. B. Yu, G. Q. Lo, and D. L. Kwong, “Multi-channel silicon photonic receiver based on ring-resonators,” Opt. Express 18(13), 13510–13515 (2010). [CrossRef] [PubMed]

24.

S. Park, K. J. Kim, I. G. Kim, and G. Kim, “Si micro-ring MUX/DeMUX WDM filters,” Opt. Express 19(14), 13531–13539 (2011). [CrossRef] [PubMed]

25.

R. Terawaki, Y. Takahashi, M. Chihara, Y. Inui, and S. Noda, “Ultrahigh-Q photonic crystal nanocavities in wide optical telecommunication bands,” Opt. Express 20(20), 22743–22752 (2012). [CrossRef] [PubMed]

26.

D. F. Edwards, “Silicon (Si),” in Handbook of Optical Constants of Solids vol. 1 E. D. Palik, ed. (Academic Press, 1985).

27.

H. Nishi, T. Tsuchizawa, R. Kou, H. Shinojima, T. Yamada, H. Kimura, Y. Ishikawa, K. Wada, and K. Yamada, “Monolithic integration of a silica AWG and Ge photodiodes on Si photonic platform for one-chip WDM receiver,” Opt. Express 20(8), 9312–9321 (2012). [CrossRef] [PubMed]

28.

T. Asano, B. S. Song, and S. Noda, “Analysis of the experimental Q factors (~ 1 million) of photonic crystal nanocavities,” Opt. Express 14(5), 1996–2002 (2006). [CrossRef] [PubMed]

29.

H. Hagino, Y. Takahashi, Y. Tanaka, T. Asano, and S. Noda, “Effects of fluctuation in air hole radii and positions on optical characteristics in photonic crystal heterostructure nanocavities,” Phys. Rev. B 79(8), 085112 (2009). [CrossRef]

30.

C. Manolatou, M. J. Khan, S. Fan, P. R. Villeneuve, H. A. Haus, and J. D. Joannopoulos, “Coupling of modes analysis of resonant channel add-drop filters,” IEEE J. Quantum Electron. 35(9), 1322–1331 (1999). [CrossRef]

31.

C. J. Chen, J. Zheng, T. Gu, J. F. McMillan, M. Yu, G. Q. Lo, D. L. Kwong, and C. W. Wong, “Selective tuning of high-Q silicon photonic crystal nanocavities via laser-assisted local oxidation,” Opt. Express 19(13), 12480–12489 (2011). [CrossRef] [PubMed]

32.

A. Yokoo, T. Tanabe, E. Kuramochi, and M. Notomi, “Ultrahigh-Q nanocavities written with a nanoprobe,” Nano Lett. 11(9), 3634–3642 (2011). [CrossRef] [PubMed]

33.

S. W. Jeon, J. K. Han, B. S. Song, and S. Noda, “Glass-embedded two-dimensional silicon photonic crystal devices with a broad bandwidth waveguide and a high quality nanocavity,” Opt. Express 18(18), 19361–19366 (2010). [CrossRef] [PubMed]

OCIS Codes
(060.4230) Fiber optics and optical communications : Multiplexing
(130.3120) Integrated optics : Integrated optics devices
(250.3140) Optoelectronics : Integrated optoelectronic circuits
(230.5298) Optical devices : Photonic crystals

ToC Category:
Integrated Optics

History
Original Manuscript: January 13, 2014
Revised Manuscript: February 13, 2014
Manuscript Accepted: February 13, 2014
Published: February 20, 2014

Citation
Yasushi Takahashi, Takashi Asano, Daiki Yamashita, and Susumu Noda, "Ultra-compact 32-channel drop filter with 100 GHz spacing," Opt. Express 22, 4692-4698 (2014)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-22-4-4692


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References

  1. Y. Akahane, T. Asano, B. S. Song, S. Noda, “High-Q photonic nanocavity in a two-dimensional photonic crystal,” Nature 425(6961), 944–947 (2003). [CrossRef] [PubMed]
  2. B. S. Song, S. Noda, T. Asano, Y. Akahane, “Ultra-High-Q photonic double-heterostructure nanocavity,” Nat. Mater. 4(3), 207–210 (2005). [CrossRef]
  3. Y. Taguchi, Y. Takahashi, Y. Sato, T. Asano, S. Noda, “Statistical studies of photonic heterostructure nanocavities with an average Q factor of three million,” Opt. Express 19(12), 11916–11921 (2011). [CrossRef] [PubMed]
  4. H. Sekoguchi, Y. Takahashi, T. Asano, S. Noda, “Photonic crystal nanocavity with a Q-factor of ~9 million,” Opt. Express 22(1), 916–924 (2014). [CrossRef] [PubMed]
  5. E. Kuramochi, M. Notomi, S. Hughes, A. Shinya, T. Watanabe, L. Ramunno, “Disorder-induced scattering loss of line-defect waveguides in photonic crystal slabs,” Phys. Rev. B 72(16), 161318 (2005). [CrossRef]
  6. T. Tanabe, H. Sumikura, H. Taniyama, A. Shinya, M. Notomi, “All-silicon sub-Gb/s telecom detector with low dark current and high quantum efficiency on chip,” Appl. Phys. Lett. 96(10), 101103 (2010). [CrossRef]
  7. L. D. Haret, X. Checoury, Z. Han, P. Boucaud, S. Combrié, A. De Rossi, “All-silicon photonic crystal photoconductor on silicon-on-insulator at telecom wavelength,” Opt. Express 18(23), 23965–23972 (2010). [CrossRef] [PubMed]
  8. T. Tanabe, K. Nishiguchi, E. Kuramochi, M. Notomi, “Low power and fast electro-optic silicon modulator with lateral p-i-n embedded photonic crystal nanocavity,” Opt. Express 17(25), 22505–22513 (2009). [CrossRef] [PubMed]
  9. K. Debnath, L. O’Faolain, F. Y. Gardes, A. G. Steffan, G. T. Reed, T. F. Krauss, “Cascaded modulator architecture for WDM applications,” Opt. Express 20(25), 27420–27428 (2012). [CrossRef] [PubMed]
  10. Y. Takahashi, Y. Inui, M. Chihara, T. Asano, R. Terawaki, S. Noda, “A micrometre-scale Raman silicon laser with a microwatt threshold,” Nature 498(7455), 470–474 (2013). [CrossRef] [PubMed]
  11. M. Shinkawa, N. Ishikura, Y. Hama, K. Suzuki, T. Baba, “Nonlinear enhancement in photonic crystal slow light waveguides fabricated using CMOS-compatible process,” Opt. Express 19(22), 22208–22218 (2011). [CrossRef] [PubMed]
  12. H. C. Nguyen, N. Yazawa, S. Hashimoto, S. Otsuka, T. Baba, “Sub-100 μm Photonic Crystal Si Optical Modulators: Spectral, Athermal, and High-Speed Performance,” IEEE J. Sel. Top. Quantum Electron. 19(6), 127 (2013). [CrossRef]
  13. S. Fan, P. R. Villeneuve, J. D. Joannopoulos, “Channel drop tunneling through localized states,” Phys. Rev. Lett. 80(5), 960–963 (1998). [CrossRef]
  14. S. Noda, A. Chutinan, M. Imada, “Trapping and emission of photons by a single defect in a photonic bandgap structure,” Nature 407(6804), 608–610 (2000). [CrossRef] [PubMed]
  15. A. Chutinan, M. Mochizuki, M. Imada, S. Noda, “Surface-emitting channel drop filters using single defects in two-dimensional photonic crystal slabs,” Appl. Phys. Lett. 79(17), 2690–2692 (2001). [CrossRef]
  16. B. S. Song, S. Noda, T. Asano, “Photonic devices based on in-plane hetero photonic crystals,” Science 300(5625), 1537 (2003). [CrossRef] [PubMed]
  17. Y. Akahane, T. Asano, B.-S. Song, S. Noda, “Investigation of high-Q channel drop filters using donor-type defects in two-dimensional photonic crystal slabs,” Appl. Phys. Lett. 83(8), 1512–1514 (2003). [CrossRef]
  18. Y. Akahane, T. Asano, H. Takano, B. S. Song, Y. Takana, S. Noda, “Two-dimensional photonic-crystal-slab channeldrop filter with flat-top response,” Opt. Express 13(7), 2512–2530 (2005). [CrossRef] [PubMed]
  19. H. Takano, B. S. Song, T. Asano, S. Noda, “Highly efficient multi-channel drop filter in a two-dimensional hetero photonic crystal,” Opt. Express 14(8), 3491–3496 (2006). [CrossRef] [PubMed]
  20. A. Shinya, S. Mitsugi, E. Kuramochi, M. Notomi, “Ultrasmall multi-port channel drop filter in two-dimensional photonic crystal on silicon-on-insulator substrate,” Opt. Express 14(25), 12394–12400 (2006). [CrossRef] [PubMed]
  21. B. S. Song, T. Nagashima, T. Asano, S. Noda, “Resonant-wavelength control of nanocavities by nanometer-scaled adjustment of two-dimensional photonic crystal slab structures,” IEEE Photon. Technol. Lett. 20(7), 532–534 (2008). [CrossRef]
  22. Q. Fang, T. Y. Liow, J. F. Song, K. W. Ang, M. B. Yu, G. Q. Lo, D. L. Kwong, “WDM multi-channel silicon photonic receiver with 320 Gbps data transmission capability,” Opt. Express 18(5), 5106–5113 (2010). [CrossRef] [PubMed]
  23. Q. Fang, Y. T. Phang, C. W. Tan, T. Y. Liow, M. B. Yu, G. Q. Lo, D. L. Kwong, “Multi-channel silicon photonic receiver based on ring-resonators,” Opt. Express 18(13), 13510–13515 (2010). [CrossRef] [PubMed]
  24. S. Park, K. J. Kim, I. G. Kim, G. Kim, “Si micro-ring MUX/DeMUX WDM filters,” Opt. Express 19(14), 13531–13539 (2011). [CrossRef] [PubMed]
  25. R. Terawaki, Y. Takahashi, M. Chihara, Y. Inui, S. Noda, “Ultrahigh-Q photonic crystal nanocavities in wide optical telecommunication bands,” Opt. Express 20(20), 22743–22752 (2012). [CrossRef] [PubMed]
  26. D. F. Edwards, “Silicon (Si),” in Handbook of Optical Constants of Solids vol. 1 E. D. Palik, ed. (Academic Press, 1985).
  27. H. Nishi, T. Tsuchizawa, R. Kou, H. Shinojima, T. Yamada, H. Kimura, Y. Ishikawa, K. Wada, K. Yamada, “Monolithic integration of a silica AWG and Ge photodiodes on Si photonic platform for one-chip WDM receiver,” Opt. Express 20(8), 9312–9321 (2012). [CrossRef] [PubMed]
  28. T. Asano, B. S. Song, S. Noda, “Analysis of the experimental Q factors (~ 1 million) of photonic crystal nanocavities,” Opt. Express 14(5), 1996–2002 (2006). [CrossRef] [PubMed]
  29. H. Hagino, Y. Takahashi, Y. Tanaka, T. Asano, S. Noda, “Effects of fluctuation in air hole radii and positions on optical characteristics in photonic crystal heterostructure nanocavities,” Phys. Rev. B 79(8), 085112 (2009). [CrossRef]
  30. C. Manolatou, M. J. Khan, S. Fan, P. R. Villeneuve, H. A. Haus, J. D. Joannopoulos, “Coupling of modes analysis of resonant channel add-drop filters,” IEEE J. Quantum Electron. 35(9), 1322–1331 (1999). [CrossRef]
  31. C. J. Chen, J. Zheng, T. Gu, J. F. McMillan, M. Yu, G. Q. Lo, D. L. Kwong, C. W. Wong, “Selective tuning of high-Q silicon photonic crystal nanocavities via laser-assisted local oxidation,” Opt. Express 19(13), 12480–12489 (2011). [CrossRef] [PubMed]
  32. A. Yokoo, T. Tanabe, E. Kuramochi, M. Notomi, “Ultrahigh-Q nanocavities written with a nanoprobe,” Nano Lett. 11(9), 3634–3642 (2011). [CrossRef] [PubMed]
  33. S. W. Jeon, J. K. Han, B. S. Song, S. Noda, “Glass-embedded two-dimensional silicon photonic crystal devices with a broad bandwidth waveguide and a high quality nanocavity,” Opt. Express 18(18), 19361–19366 (2010). [CrossRef] [PubMed]

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