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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 15, Iss. 14 — Jul. 9, 2007
  • pp: 8566–8575
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Large-area, three-state, binary amplitude and binary phase vertical-cavity multiple quantum well electroabsorption modulator

Stéphane Junique, Qin Wang, Susanne Almqvist, Bertrand Noharet, and Jan Y. Andersson  »View Author Affiliations


Optics Express, Vol. 15, Issue 14, pp. 8566-8575 (2007)
http://dx.doi.org/10.1364/OE.15.008566


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Abstract

We present the design and characterization of a large optical modulator array based on GaAs multiple quantum wells for amplitude and phase modulation. The device shows two high-reflectance states with a phase difference close to 180° for use as a binary phase modulator. It also shows a third, low-reflectance state for use as an amplitude modulator. It is segmented into 64 pixels in a single row, giving an active area of 2mm × 5mm. We discuss the device performance as a ternary binary amplitude and binary phase modulator, including contrast ratio and uniformity, and show that a voltage swing of only 5V is needed to drive it.

© 2007 Optical Society of America

1. Introduction

The Quantum-Confined Stark Effect (QCSE) that occurs in semiconductor quantum wells (QW) has been extensively exploited to make high-speed optical amplitude modulators in GaAs- and InP-based materials [1–5

1. K. Wakita, I. Kotaka, O. Mitomi, H. Asai, Y. Kawamura, and M. Naganuma, “High-speed InGaAlAs /InAlAs Multiple Quantum Well Optical Modulators,” J. Lightwave Technol. 8, 1027–1032 (1990). [CrossRef]

]. The vertical-access variant presents many advantages over the longitudinal one. It allows the fabrication of large-area [6

6. G. C. Gilbreath, W. S. Rabinovich, T. J. Meehan, M. J. Vilcheck, R. Mahon, R. Burris, M. Ferraro, I. Solkolsky, J. A. Vasquez, C. S. Bovais, K. Cochrell, K. C. Goins, R. Barbehenn, D. S. Katzer, K. Ikossi-Anastasiou, and M. J. Montes, “Large-aperture multiple quantum well modulating retroreflector for free-space optical data transfer on unmanned aerial vehicles,” Opt. Eng. 40, 1348–1356 (2001). [CrossRef]

,7

7. Qin Wang, Stéphane Junique, Daniel Ågren, Bertrand Noharet, and Jan Y. Andersson, “Fabry-Pérot Electroabsorption Modulators for High-Speed Free-Space Optical Communication,” IEEE Photon. Technol. Lett. 16, 1471–1473 (2004). [CrossRef]

] and two-dimensional arrays [8–11

8. U. Efron and G. Livescu, “Multiple quantum well spatial light modulators,” in Spatial light modulator technology: materials, devices and applications, Uzi Efron, ed. (Marcel Dekker, Inc., 1994).

] for example, and is insensitive to the polarization of the incident light beam. Resonant cavity structures obtained by embedding the multiple quantum wells (MQW) between two mirrors (for example Distributed Bragg Reflectors (DBR) or metallic layers) are easy to fabricate, and significantly increase the contrast ratio of amplitude modulators [12–14

12. B. Pezeshki, D. Thomas, and J. S. Harris Jr, “Optimization of modulation ratio and insertion loss in reflective electroabsorption modulators,” Appl. Phys. Lett. 57, 1491–1492 (1990). [CrossRef]

].

There are, however, a range of applications that would benefit from the modulation speed delivered by MQW optical modulators, but need phase modulation in addition to or instead of amplitude modulation. Such applications include free-space optical communication where phase keying is more immune to atmospheric perturbations than amplitude modulation; beam steering where the zero-order diffraction cannot be suppressed using purely amplitude modulation; optical signal processing where binary phase and ternary binary amplitude and binary phase modulators would provide dramatic improvements over binary amplitude MQW modulators (in terms of coding domain); liquid crystal-based binary, phase-only modulators (in terms of modulation speed) in some optical processor architectures. Indeed, in systems such as the VanderLugt type of optical correlators, a ternary coding domain would allow correlation filters to be encoded using time-averaged, pseudo-random encoding [15

15. B. Noharet and S. Junique, “Multiple quantum well spatial light modulators for correlation-based processors,” in Optoelectronic Information Processing: Optics for Information Systems, P. Réfrégier, B. Javidi, C. Ferreira, and S. Vallmitjana, eds. (SPIE, Bellingham, Wash., 2001), pp. 314–364.

].

In a reflection resonant-cavity MQW modulator, phase modulation can be obtained through two effects. First is the change in refractive index that takes place in the MQW structure when the absorption changes, as described by the Kramers-Krönig relation. This effect is used in longitudinal phase modulators but is rather weak, necessitating an active region of hundreds of micrometers [16–18

16. K. Wakita, I. Kotaka, and H. Asai, “High-speed InGaAlAs/InAlAs multiple quantum well electrooptic phase modulators with bandwidth in excess of 20GHz,” IEEE Photon Technol. Lett. 4, 29–31 (1992). [CrossRef]

]. The other effect is due to the resonant cavity, and was described by Pezeshki [19

19. B. Pezeshki, G. A. Williams, and J. S. Harris Jr, “Optical phase modulator utilizing electroabsorption in a Fabry-Perot cavity,” Appl. Phys. Lett. 60, 1061–1063 (1992). [CrossRef]

] and Trezza [20

20. J. A. Trezza and J. S. Harris, “Creation and optimization of vertical cavity phase flip modulators,” J. Appl. Phys. 75, 4878–4884 (1994). [CrossRef]

]. A simplified view is the observation that the difference in path length between the front and the back mirror of the cavity corresponds to a phase difference of 180° at the resonant wavelength. If the reflected beam comes predominantly from the back mirror in one state (because the front mirror has a lower reflectance), and comes predominantly from the front mirror in the other state (because most of the light is absorbed by the MQW inside the cavity), then a phase difference of 180° should be observed between the two states. In practice, both effects are present and the cavity resonance is not in tune between the two states, with the consequence that coupled amplitude and phase modulation is usually observed in vertical-cavity modulators. Pezeshki [19

19. B. Pezeshki, G. A. Williams, and J. S. Harris Jr, “Optical phase modulator utilizing electroabsorption in a Fabry-Perot cavity,” Appl. Phys. Lett. 60, 1061–1063 (1992). [CrossRef]

] and Trezza [20

20. J. A. Trezza and J. S. Harris, “Creation and optimization of vertical cavity phase flip modulators,” J. Appl. Phys. 75, 4878–4884 (1994). [CrossRef]

,21

21. J. A. Trezza and J. S. Harris, “Two-state electrically controllable phase diffraction grating using arrays of vertical-cavity phase flip modulators,” IEEE Photon Technol. Lett. 8, 1211–1213 (1996). [CrossRef]

] have demonstrated vertical-cavity phase modulators on small, single-pixel devices.

We have developed a large-area modulator array for amplitude and phase modulation. The device presents two high-reflectance states with a phase difference close to 180°, for use as a binary phase modulator. It also presents a third, low reflectance state for use as an amplitude modulator.

2. Device design

The device structure is composed of a resonant cavity, containing a QW structure sandwiched between two DBRs. The structure was modeled using the thin-film optical transfer-matrix technique [22

22. H. A. Macleod, Thin-Film Optical Filters (Institute of Physics, Bristol, 2001). [CrossRef]

,23

23. P. Yeh, Optical waves in layered media (John Wiley Sons, Inc., 1988).

]. The properties of the QW structure were calculated using the envelope-function approximation (see [24

24. G. Bastard, Wave Mechanics Applied to Semiconductor Heterostructures (Les Éditions de Physique, Paris, 1988).

], chap. III). The absorption profile of the QW structure was obtained for each electric field of interest by discretizing a structure comprising a well and its two barriers, in order to find the energy levels and wave-functions in the conduction and valence bands. Then the excitonic energies were calculated using a variational procedure on a Gaussian basis set as described by Bastard ([24

24. G. Bastard, Wave Mechanics Applied to Semiconductor Heterostructures (Les Éditions de Physique, Paris, 1988).

] chap. IV and VIII). The change in refractive index as a function of applied voltage was then obtained from the absorption profiles using the Kramers-Krönig relationship. These properties were integrated into our thin-film optics model by considering the QW structure as a single layer with a complex refractive index.

To allow both pure amplitude and pure phase modulation, the modulator structure needs to be operated at a wavelength λ0 and have two high-reflectance states with a phase difference close to 180°, and a third low-reflectance state.

At λ0, located in the vicinity of the cavity’s resonant wavelength, there is negligible absorption inside the cavity when no bias is applied. The light is predominantly reflected from the back mirror (which is stronger than the front mirror), and the device reflectance at λ0 is suitable for a high-reflectance state.

For a low-reflectance state to exist, the cavity resonance has to be located at a wavelength close to the heavy-hole excitonic absorption so that when an electric field is applied to the device, the excitonic peak is red-shifted towards the resonant wavelength, thus decreasing the device reflectance in that wavelength region. The operating wavelength for amplitude modulation λa also has to be chosen in the same region. In this state, the front- and back-mirror appear to be of equal reflectivity, thus balancing the Fabry-Perot resonator, because the cavity losses at λa compensate for the higher back-mirror reflectance. The applied voltages corresponding to the initial high-reflectance and the low-reflectance states can be designated V1 and V2 respectively, with 0≥V 1V 2 (the device is reverse-biased).

The conditions required to obtain two high-reflectance states with a large phase difference are that the front mirror of the structure be dominant in one state, and the back mirror be dominant in the other state, as described in the introduction. This implies that the operating wavelength for phase modulation λp must be at or close to the cavity resonance, and that the resonance itself be close to the excitonic absorption peak, in order to allow large changes in absorption to take place at λp. The back mirror dominates in the state with the applied bias Va, and the front mirror dominates (because of cavity losses at λp) at bias Vb, where 0 ≥ VaVb.

The conditions for amplitude and for phase modulation appear qualitatively compatible. There is a need for an increase in cavity absorption at the operating wavelength between the back-mirror dominating state (at V 1 = Va), the balanced state (at V2) and the front-mirror dominating state (at Vb) where 0 ≥ V 1V 2Vb. Quantitatively, the optimal exciton-cavity separation is lower for phase modulation than for amplitude modulation. In order to allow high-enough cavity losses in the state dominated by the front-mirror, a careful compromise is necessary. Also, it must be ensured that the amplitude and phase operating wavelengths are the same. There is no guarantee that the wavelength providing the requested phase shift for phase modulation can provide a good low-amplitude state, since the cavity resonance shifts with the applied voltage due to the electro-refractive effect in the QW structure.

The modulator structure was designed for amplitude modulation, but its compatibility with phase modulation was kept in mind. It was optimized by choosing the right number of wells in the QW structure, to allow all three operation states to be achieved with a voltage swing not larger than 5V. The Fabry-Perot resonance was finely adjusted by adding/removing pairs of layers to the front Bragg mirror, and the cavity length by changing the thickness of the n-doped buffer layer located between the QW structure and the front mirror. These two parameters permitted control of the contrast ratio between the first high-reflectance state and the low-reflectance state, and the degree of phase difference between the two high-reflectance states. Once a satisfactory structure was achieved, the results were applied to our wafer-level growth calibration tools.

Although growth uniformity has been improved dramatically during the recent years, especially for production runs [25

25. H. Malm, C. Asplund, S. Becanovic, J. Borgling, A. Parekh, and B. Hirschauer, “Advanced process control for high quality R&D and production of MOVPE material by RealTemp,” J. Cryst. Growth 248, 229–234 (2003). [CrossRef]

], layer thicknesses vary across the wafer. We grow our structures on 4 inch wafers and there is a clear variation of features such as the reflectance wavelength range of Bragg mirrors across the wafer. The variation is even more severe concerning the cavity resonance, for which variations across large devices can often be observed [11

11. Stéphane Junique, Qin Wang, Susanne Almqvist, Jianhua Guo, Henk Martijn, Bertrand Noharet, and Jan Y. Andersson, “GaAs-based multiple-quantum-well spatial light modulators fabricated by a wafer-scale process,” Appl. Opt. 44, 1635–1641 (2005). [CrossRef] [PubMed]

]. The structure growth was calibrated to allow most of the devices to achieve at least a moderate amplitude modulation, by allowing the cavity-exciton separation to be larger rather than smaller than the one needed for the three-state modulator. It was expected that for one specific value of the exciton-cavity separation, phase modulation would also be achieved.

Electrically, the device is a p-i-n diode, with the QW structure located in the intrinsic region and the p-doped region at the bottom of the structure. The QW structure is composed of 60 periods of 70Å GaAs wells and 60Å Al0.3Ga0.7As barriers. This produces no noticeable coupling between the wells. The back reflector is composed of 25 pairs of p-doped λ/4 Al0.2Ga0.8As/Al0.69Ga0.31 As layers. The front mirror is composed of 5 pairs of n-doped λ/4 Al0.22Ga0.78As/Al0.77Ga0.23As layers. An n-doped Al0.22Ga0.78As layer is located between the QW structure and the front mirror, and is used to adjust the cavity length during the design phase and also as a common n-contact layer.

The structure was grown in a Metal-Organic Vapor Phase Epitaxy (MOVPE) system on a 4-inch wafer. The device fabrication process has been described elsewhere [26

26. Qin Wang, Stéphane Junique, Daniel Ågren, Susanne Almqvist, and Bertrand Noharet, “Arrays of vertical-cavity electroabsorption modulators for parallel signal processing,” Opt. Express 13, 3323–3330 (2005). [CrossRef] [PubMed]

]. Geometrically, the device consists of two rows containing 64 rectangle-shaped pixels each, separated by 1mm of unprocessed material. Each row is 2mm in width and just over 5mm-long in the segmented direction, with pixels of 2mm × 78μm in size. A picture of a mounted device is shown in Fig. 1. The modulator array was flip-chip bonded to a silicon carrier with individual contact stripes to each pixel. The device utilizes discrete electronics on an external board. A sketch of the modulator array hybridized to its silicon carrier is shown on the left-hand side of Fig. 2. The upper, n-doped part of the chip is a continuous layer and contains a common contact, whereas the lower part comprised of the intrinsic MQW structure and the p-doped back mirror is segmented into pixels with independent p-side contacts. A picture of a corner of the modulator chip before flip-chip bonding is shown on the right-hand side of Fig. 2.

The device was developed with low driving voltage in mind and does not require more than 5V of voltage swing. The voltage requirements and type of contact make the device design compatible with the use of Application-Specific Integrated Circuits (ASICs) fabricated by standard processes, and the device could be hybridized to such driving electronics by flip-chip mounting techniques if the need arose.

To perform our experiments on phase modulation, we selected a device on the wafer with a cavity resonance at 853nm, which our modeling predicted should be suitable for both amplitude and phase modulation. We then studied one of the modulator rows on the device.

Fig. 1. Picture of a mounted device. It contains two rows of 64 pixels. Each row size is 2mm × 5mm, and each pixel 2mm × 78μm. The modulator chip was hybridized to a silicon carrier using flip-chip bonding technology, to allow independent electrical access to all pixels. In our experiment, only the bottom row of modulators was characterized.
Fig. 2. Left: Sketch of the corner of the modulator array hybridized to its silicon carrier, showing the individual p-doped Bragg mirrors, intrinsic quantum well regions, and the n- doped, common contact region of the modulator array; the left-hand mesa is covered by a metal layer (shown in grey) all the way down to the n-doped region and is used as a common contact;. The other two mesas shown are active pixels. And right: microscope picture showing a top-view of the modulator corner before flip-chip bonding to the silicon carrier, with common contacts and active pixels.

3. Experimental results

The device was characterized in reflectance using a fiber-based set-up. A pigtailed superluminescent diode with a central wavelength of 842nm and a full width at half maximum of 27nm was used as the light source. The light was sent through an arm of a 50/50 optical fiber splitter to an optical fiber collimator, which illuminated the modulator with an angle of incidence orthogonal to the device surface. The illuminated area was circular, with a diameter below 0.5mm. The reflected beam was coupled back to the collimator, collected in the second arm of the splitter and sent to an optical spectrum analyzer.

The reflectance was measured at three points centered vertically on the pixel row, at the left end, center and right end of the row, in order to check the uniformity. In the unbiased state, we found a cavity variation of 0.6nm or 0.07% over the device, with cavity lengths of 852.6nm, 852.7nm, and 853.2nm respectively for the left, center, and right positions. The reflectance at the cavity dip also increased from 13% at the left point to 23% and 25% at the central and right points respectively. The absorption peak corresponding to the exciton was located at 847nm, giving a cavity-exciton separation close to 6nm.

Figure 3 shows the reflectance profile at the center of the device, for voltages between 0V and -7V. When a reverse bias is applied, the reflectance at the cavity dip decreases to reach a minimum at -4V to -6V (-5V on the Fig.), depending on the position on the device, as the excitonic peak is shifted towards the resonance wavelength. It also results in a slight red-shift of the cavity and an increased cavity width. As the bias is increased again towards -10V, the reflectance increases again, but the cavity resonance is blue-shifted by 2nm. The cavity shifts are expected, and are due to the change in refractive index in the MQW structure, induced by the electric field. Between -7V and -10V, no further change of the device reflectance is observed.

Fig. 3. Reflectance profile at the center of the array, showing how the exciton peak red-shifts from 847nm (0V) to 851nm (-7V), while the resonant cavity first red-shifts from 853nm (0V) to 853.5nm (-5V), then blue-shifts to 851nm (-7V).

By comparing the measured reflectance with our computer model, we determined that the optimal operating wavelength to obtain a phase modulation close to 180° and a reasonable amplitude modulation should be at λ0 = 853nm. Figure 4 shows the device reflectance at λ0 as a function of the applied bias, for all three measurement points. Each independent area reaches a maximum contrast ratio (CR) in excess of 8:1 at λ0. Using a common voltage V2 = -5V for the low-reflectance state, CRs over 6:1, 5:1 and 3.5:1 are observed at the three measurement points for high-reflectance states at V1 = 0V, V1 = -2V and Vc = -7V, respectively.

The device was characterized in phase using a modified Michelson interferometer set-up, with one arm using the device as the reflector. A tunable semiconductor laser adjusted to λ0 was used for the illumination. The interferometer was aligned to provide vertical, high-visibility interference fringes. The interferometric pattern was expanded using a divergent lens, and captured piece-wise using a CCD camera. We measured the shift of vertically-aligned interference fringes to evaluate the phase modulation. The device length contained 11 light interference fringes in total, resulting in 10 measurement areas, each located between two light interference fringes and containing approximately 6 modulator pixels. We estimate the measurement accuracy of the phase shift to be better than +/- 10°, limited by the camera resolution. Figure 5 shows the phase variation with the applied voltage at each measurement point. The phase of the reflected beam increases slowly between 0V and -2V, then increases at a faster pace between -2V and -6V, and is almost constant for applied voltages between -6.5V and -8V. Over the device, the phase variation ranges from 215° to 310° for a voltage change of 0V to -7V, or 175° to 265° for -2V to -7V. It is advantageous to choose high-reflectance states at V1 = -2V and Vc = -7V, because the phase difference is closer to 180°, and also because the voltage swing is only 5V.

Fig. 4. Reflectance as a function of the applied bias at three positions on the device, extreme left, center and extreme right. The illumination spot was centered vertically on the device row, with a diameter below 0.5mm.
Fig. 5. Phase shift as a function of the applied bias with regard to the phase at 0V, measured in ten contiguous regions across the modulator array.

The device uniformity as a phase modulator is shown in Fig. 6. The measured phase response at x = 4mm deviates sharply from that of neighboring measurement areas, in a way that cannot be explained by uniformity considerations. Upon further investigation, it appeared that one of the pixels in this area was shortcut. We attributed the misbehavior to this defective pixel and ignored this measurement area in our device analysis. The measurement area located at 1.5mm presents a similarly lower phase modulation. We did not notice any electrical problem with a pixel in that area and do not know the cause for this lower modulation.

Fig. 6. Phase difference between chosen applied biases, showing the uniformity across the modulator array. The device region marked as x=4mm contains a shortcut pixel, to which we attribute the lower observed phase modulation.

Except at position 4mm, the phase modulation shows a uniformity variation below 25° between positions at 2mm and 5mm, providing a phase modulation between 242° and 264°, 230° and 250°, and 193° and 218° for voltage swings of -2V to -7V, -2.5 to -7V and -3 to -7V, respectively. The left part of the device shows a smaller, less uniform phase modulation for similar voltage swings. This is in line with the reflectance measurements. The reflectance curves for the central and right measurement points are close together between 0V and -5V, whereas the curve for the left-hand point is further away, illustrating the effect of the device non-uniformity.

4. Discussion

These measurements illustrate the potential of such a device design as a ternary binary amplitude and binary phase modulator. The central measurement point shows a phase modulation of 255° and a constant reflectance of 23% ± 1% for operating states at -2V and -7V, producing a binary phase modulation. Using -5V as the low-reflectance state with either of the other two, a binary amplitude modulator is achieved with a contrast ratio in excess of 13:1. If a phase modulation closer to 180° is required, the bias for the first state can be changed from -2V to -3V, which decreases the reflectance to 16%. The reflectance for the matching phase state can be brought to the same level by adjusting the bias to approximately -6.6V (obtained by linear interpolation between -6V and -7V). The device then provides a phase modulation of 185°, at the expense of a lower amplitude modulation. Through use of the same low-reflectance state as before, the CR lies at 9.5:1.

It is possible to extend this ternary modulation to the full area contained between the central and right measurement points by adjusting the bias used for each pixel. The reflectance at the right-hand measurement point is 16% and 15% for biases of -3V and -7V respectively. The phase difference between these two states is 220°. Using -6V for the low-reflectance state at the right-hand measurement point, an amplitude modulation with a CR of 7:1 is obtained, producing once more the ternary binary amplitude and binary phase modulation. Similar corresponding conditions are expected to be achievable at any location between these two measurement areas. Furthermore, the phase modulation in the whole area located between these two measurement points is expected to be contained between these limits, giving a phase modulation of 185° to 220°, or a phase uniformity of 35°, at a constant reflectance of 16%.

The left-hand measurement point on the device provides a reflectance of 15% at -2V and at approximately -6.2V (obtained by linear interpolation between -6V and -7V). The phase difference between these two states is 170°. Using -4V for the low-amplitude level, a CR of 7:1 is obtained. Supposing that the optical performance at any position on the device is within the range limited by these three measurement points, and allowing individual bias voltages for each pixel, a binary phase modulation is achievable through the full device, with a phase shift contained between 170° and 220°.

Fig. 7. Coding domains measured between -2V and -8V in steps of 1V at the device left (circles), center (crosses) and right (squares) measurement spots, at 853nm. The measurement points are plotted as complex numbers in the complex plane. The measured reflectance is used as the modulus, and the phase at -2V is taken as the phase origin for each of the three measurement locations on the device.

The optical properties demonstrated with this device are particularly well adapted to some optical signal processing applications, for which ternary binary amplitude and binary phase modulation would provide a huge gain over (even grey-level) amplitude-only modulation [15

15. B. Noharet and S. Junique, “Multiple quantum well spatial light modulators for correlation-based processors,” in Optoelectronic Information Processing: Optics for Information Systems, P. Réfrégier, B. Javidi, C. Ferreira, and S. Vallmitjana, eds. (SPIE, Bellingham, Wash., 2001), pp. 314–364.

]. The amplitude and phase modulation are plotted as a coding domain in Fig. 7 for the device center, left and right spots. In all cases, two high-reflectance states with a phase difference close to 180°, as well as a low-reflectance state exist. Two-dimensional modulator arrays with an active area comparable to that of our device could be fabricated. They would allow the time-averaged, pseudo-random encoding technique to be used in optical signal processing systems, at the speed attainable by MQW optical modulators.

The optical properties of the device demonstrate that large-area MQW-based phase modulator arrays can be fabricated. They also show that device uniformity is the main limitation, a cavity variation of 0.6nm causing the phase modulation between states at -3V and -7V to vary from 85° to 220° over the device. If we regard this span as the maximum acceptable for a phase modulator, the tolerance of phase modulators to uniformity variations is an order of magnitude lower than for amplitude modulators using a resonant-cavity design, where cavity variations of several nanometers still permit a sizable intensity modulation.

5. Conclusion

We have presented a large, one-dimensional modulator array of 2mm × 5mm. The design constraints of an amplitude modulator and of a phase modulator have been discussed, as well as the compromises that these two sets of constraints imply for a device with both capabilities. We have characterized the device in amplitude and, at a suitable wavelength, we have characterized its phase modulation. In particular, we have shown that pure phase modulation can be obtained, with the modulation ranging between 170° and 220° on the device. This range is due to variations in the resonant cavity position across the device. We have also discussed the device performance as a ternary binary amplitude and binary phase modulator. We have shown that a voltage swing of only 5V is needed to drive it, which allows standard electronic circuitry to be used. Since the device is also compatible with flip-chip bonding technology, it could be hybridized to an ASIC for applications with high requirements regarding compacture.

Acknowledgments

The authors wish to thank Hedda Malm, Carl Asplund, Smilja Becanovic, and Jan Borglind for the MOVPE growth of the modulator structure, and Leif Kjellberg for his help with the electronics. Part of this work was supported by the EU IST-2001-37435 project. Stéphane Junique also wishes to thank The Swedish Knowledge Foundation, KKS, for a support grant.

References and links

1.

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P. Zouganeli and G. Parry, “Evaluation of the Tolerance of Asymmetric Fabry-Perot Modulators with Respect to Realistic Operating Conditions,” IEEE J. Quantum Electron. 31, 1140–1151 (1995). [CrossRef]

15.

B. Noharet and S. Junique, “Multiple quantum well spatial light modulators for correlation-based processors,” in Optoelectronic Information Processing: Optics for Information Systems, P. Réfrégier, B. Javidi, C. Ferreira, and S. Vallmitjana, eds. (SPIE, Bellingham, Wash., 2001), pp. 314–364.

16.

K. Wakita, I. Kotaka, and H. Asai, “High-speed InGaAlAs/InAlAs multiple quantum well electrooptic phase modulators with bandwidth in excess of 20GHz,” IEEE Photon Technol. Lett. 4, 29–31 (1992). [CrossRef]

17.

Y. Chen, J. E. Zucker, N. J. Sauer, and T. Y. Chang, “Polarization-independent strained InGaAs/InGaAlAs quantum-well phase modulators,” IEEE Photon Technol. Lett. 4, 1120–1123 (1992). [CrossRef]

18.

H. Mohseni, H. An, Z. A. Shellenbarger, M. H. Kwakernaak, and J. H. Abeles, “Highly linear and efficient phase modulators based on GaInAsP-InP three-step quantum wells,” Appl. Phys. Lett. 86, 031103 (2005). [CrossRef]

19.

B. Pezeshki, G. A. Williams, and J. S. Harris Jr, “Optical phase modulator utilizing electroabsorption in a Fabry-Perot cavity,” Appl. Phys. Lett. 60, 1061–1063 (1992). [CrossRef]

20.

J. A. Trezza and J. S. Harris, “Creation and optimization of vertical cavity phase flip modulators,” J. Appl. Phys. 75, 4878–4884 (1994). [CrossRef]

21.

J. A. Trezza and J. S. Harris, “Two-state electrically controllable phase diffraction grating using arrays of vertical-cavity phase flip modulators,” IEEE Photon Technol. Lett. 8, 1211–1213 (1996). [CrossRef]

22.

H. A. Macleod, Thin-Film Optical Filters (Institute of Physics, Bristol, 2001). [CrossRef]

23.

P. Yeh, Optical waves in layered media (John Wiley Sons, Inc., 1988).

24.

G. Bastard, Wave Mechanics Applied to Semiconductor Heterostructures (Les Éditions de Physique, Paris, 1988).

25.

H. Malm, C. Asplund, S. Becanovic, J. Borgling, A. Parekh, and B. Hirschauer, “Advanced process control for high quality R&D and production of MOVPE material by RealTemp,” J. Cryst. Growth 248, 229–234 (2003). [CrossRef]

26.

Qin Wang, Stéphane Junique, Daniel Ågren, Susanne Almqvist, and Bertrand Noharet, “Arrays of vertical-cavity electroabsorption modulators for parallel signal processing,” Opt. Express 13, 3323–3330 (2005). [CrossRef] [PubMed]

OCIS Codes
(120.5060) Instrumentation, measurement, and metrology : Phase modulation
(230.4110) Optical devices : Modulators
(230.5590) Optical devices : Quantum-well, -wire and -dot devices

ToC Category:
Optical Devices

History
Original Manuscript: March 23, 2007
Revised Manuscript: June 17, 2007
Manuscript Accepted: June 18, 2007
Published: June 25, 2007

Citation
Stéphane Junique, Qin Wang, Susanne Almqvist, Bertrand Noharet, and Jan Y. Andersson, "Large–area, three–state, binary amplitude and binary phase vertical–cavity multiple quantum well electroabsorption modulator," Opt. Express 15, 8566-8575 (2007)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-15-14-8566


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References

  1. K. Wakita, I. Kotaka, O. Mitomi, H. Asai, Y. Kawamura, and M. Naganuma, "High-speed InGaAlAs /InAlAs Multiple Quantum Well Optical Modulators," J. Lightwave Technol. 8, 1027-1032 (1990). [CrossRef]
  2. F. Devaux, P. Bordes, A. Ougazzaden, M. Carré, and F. Huet, "Experimental optimisation of MQW electroabsorption modulators with up to 40GHz bandwidths," Electron Lett. 30, 1347-1348 (1994). [CrossRef]
  3. R. Spickermann, N. Dagli and M. G. Peters, "GaAs/AlGaAs electro-optic modulator with bandwidth >40GHz," Electron Lett. 31, 915-916 (1995). [CrossRef]
  4. K. K. Loi, L. Shen, H. H. Wieder, and W. S. C. Chang, "Electroabsorption Waveguide Modulators at 1.3 µm Fabricated on GaAs Substrates," IEEE Photon. Technol. Lett. 9, 1229-1231 (1997). [CrossRef]
  5. H. Liu, C.-Chung Lin, and J. S. Harris, Jr., "High-speed, dual-function vertical cavity multiple quantum well modulators and photodetectors for optical interconnects," Opt. Eng. 40, 1186-1191 (2001). [CrossRef]
  6. G. C. Gilbreath, W. S. Rabinovich, T. J. Meehan, M. J. Vilcheck, R. Mahon, R. Burris, M. Ferraro, I. Solkolsky, J. A. Vasquez, C. S. Bovais, K. Cochrell, K. C. Goins, R. Barbehenn, D. S. Katzer, K. Ikossi-Anastasiou, and M. J. Montes, "Large-aperture multiple quantum well modulating retroreflector for free-space optical data transfer on unmanned aerial vehicles," Opt. Eng. 40, 1348-1356 (2001). [CrossRef]
  7. Q. Wang, S. Junique, D. Ågren, B. Noharet, and J. Y. Andersson, "Fabry-Pérot Electroabsorption Modulators for High-Speed Free-Space Optical Communication," IEEE Photon. Technol. Lett. 16, 1471-1473 (2004). [CrossRef]
  8. U. Efron and G. Livescu, "Multiple quantum well spatial light modulators," in Spatial light modulator technology: materials, devices and applications, Uzi Efron, ed. (Marcel Dekker, Inc., 1994).
  9. K. W. Goossen, J. A. Walker, L. A. D’Araso, S. P. Hui, B. Tseng, R. Leibenguth, D. Kossive, D. D. Bacon, D. Dahringer, L. M. F. Chirovsky, A. L. Lentine, and D. A. B. Miller, "GaAs MQW modulators integrated with silicon CMOS," IEEE Photon. Technol. Lett. 7, 360-362 (1995). [CrossRef]
  10. U. Arad, E. Redmard, M. Shamay, A. Averboukh, S. Levit, and U. Efron, "Development of a large high-performance 2-D array of GaAs_AlGaAs multiple quantum-well modulators," IEEE Photon. Technol. Lett. 15, 1531-1533 (2003). [CrossRef]
  11. Stéphane Junique, Qin Wang, Susanne Almqvist, Jianhua Guo, Henk Martijn, Bertrand Noharet, and Jan Y. Andersson, "GaAs-based multiple-quantum-well spatial light modulators fabricated by a wafer-scale process," Appl. Opt. 44, 1635-1641 (2005). [CrossRef] [PubMed]
  12. B. Pezeshki, D. Thomas, and J. S. HarrisJr, "Optimization of modulation ratio and insertion loss in reflective electroabsorption modulators," Appl. Phys. Lett. 57, 1491-1492 (1990). [CrossRef]
  13. P. Zouganeli, P. J. Stevens, D. Atkinson, and G. Parry, "Design Trade-offs and Evaluation of the Performance Attainable by GaAs-Al0.3Ga0.7As Asymmetric Fabry-Perot Modulators," IEEE J. Quantum Electron. 31, 927-943 (1995). [CrossRef]
  14. P. Zouganeli and G. Parry, " Evaluation of the Tolerance of Asymmetric Fabry-Perot Modulators with Respect to Realistic Operating Conditions," IEEE J. Quantum Electron. 31, 1140-1151 (1995). [CrossRef]
  15. B. Noharet and S. Junique, "Multiple quantum well spatial light modulators for correlation-based processors," in Optoelectronic Information Processing: Optics for Information Systems, P. Réfrégier, B. Javidi, C. Ferreira, and S. Vallmitjana, eds. (SPIE, Bellingham, Wash., 2001), pp. 314-364.
  16. K. Wakita, I. Kotaka, and H. Asai, "High-speed InGaAlAs/InAlAs multiple quantum well electrooptic phase modulators with bandwidth in excess of 20GHz," IEEE Photon Technol. Lett. 4, 29-31 (1992). [CrossRef]
  17. Y. Chen, J. E. Zucker, N. J. Sauer, and T. Y. Chang, "Polarization-independent strained InGaAs/InGaAlAs quantum-well phase modulators," IEEE Photon Technol. Lett. 4, 1120-1123 (1992). [CrossRef]
  18. H. Mohseni, H. An, Z. A. Shellenbarger, M. H. Kwakernaak, and J. H. Abeles, "Highly linear and efficient phase modulators based on GaInAsP-InP three-step quantum wells," Appl. Phys. Lett. 86, 031103 (2005). [CrossRef]
  19. B. Pezeshki, G. A. Williams, and J. S. Harris, Jr, "Optical phase modulator utilizing electroabsorption in a Fabry-Perot cavity," Appl. Phys. Lett. 60, 1061-1063 (1992). [CrossRef]
  20. J. A. Trezza and J. S. Harris, "Creation and optimization of vertical cavity phase flip modulators," J. Appl. Phys. 75, 4878-4884 (1994). [CrossRef]
  21. J. A. Trezza, and J. S. Harris, "Two-state electrically controllable phase diffraction grating using arrays of vertical-cavity phase flip modulators," IEEE Photon Technol. Lett. 8, 1211-1213 (1996). [CrossRef]
  22. H. A. Macleod, Thin-Film Optical Filters (Institute of Physics, Bristol, 2001). [CrossRef]
  23. P. Yeh, Optical waves in layered media (John Wiley Sons, Inc., 1988).
  24. G. Bastard, Wave Mechanics Applied to Semiconductor Heterostructures (Les Éditions de Physique, Paris, 1988).
  25. H. Malm, C. Asplund, S. Becanovic, J. Borgling, A. Parekh, and B. Hirschauer, "Advanced process control for high quality R&D and production of MOVPE material by RealTemp," J. Cryst. Growth 248, 229-234 (2003). [CrossRef]
  26. Q. Wang, S. Junique, D. Ågren, S. Almqvist and B. Noharet, "Arrays of vertical-cavity electroabsorption modulators for parallel signal processing," Opt. Express 13, 3323-3330 (2005). [CrossRef] [PubMed]

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