Quantum well modulators

The quantum-confined Stark effect (QCSE) allows very compact, high-speed, low-energy optical modulators in convenient diode structures that are also readily integrated with other optoelectronic devices, such as laser diodes. These modulators are extensively used in telecommunications. David Miller and his colleagues, in addition to discovering and explaining the QCSE mechanism, also demonstrated the first optical modulator devices based on this effect, and went on to demonstrate a wide variety of other devices, including large integrated systems. Though initially demonstrated primarily in III-V semiconductors, such as GaAs and InGaAs, more recently this mechanism has also been demonstrated in germanium quantum wells grown on silicon, offering the possibility of very high-performance optical modulators integrated in a silicon photonics platform.

Though possibly their major use is in electro-absorption modulators (also know as “EAMs”), they are also used as phase shifters in interferometric modulators such as Mach-Zehnder interferometers.

Quantum well absorption modulators

The QCSE is extensively use for absorption modulators, which change the transmitted optical power. A practical consequence of the “shifting” behavior of the transitions in the QCSE is that in a QCSE modulator, the optical absorption edge shifts relatively cleanly; by contrast in bulk semiconductors, the absorption edge essentially just broadens (by a combination of what is usually described as the Franz-Keldysh effect (FKE) – a non-excitonic model – and additional broadening of the underlying excitonic effects). This allows a modulator that can be “tuned” by applying a static bias to bring the edge near to the photon energy or wavelength of interest, and then modulated with just some small additional voltage that shifts the edge back and forward “over” the photon energy; such a mode of operation is not possible in an FKE modulator. QCSE modulators generally have strong absorption contrast also than FKE devices because of this “shifting” rather than “broadening” phenomenon.

Quantum well electro-refractive modulators

Quantum well electro-refractive modulators have been demonstrated by many groups, starting with initial device structures by Zucker et al. [pa], and followed by work by various other groups, e.g., as in [pb], [pc], [pd], [pe]. Such structure are now routinely made in advanced commercial foundry operations [pf]

Phase modulation and Mach-Zehnder interferometers with such quantum well electrorefraction have therefore been demonstrated by many groups and in commercial operations, and they constitute a particularly attractive approach in integrated III-V photonics platforms. Such phase modulation would also be possible with germanium quantum well modulators.

The effects of the refractive index changes are also readily observed in resonator modulators, such as these germanium quantum well surface-normal devices; the refractive index changes lead to shifts in the resonant peaks that greatly increase the modulation contrast in such devices.

[c] Ross M. Audet, Elizabeth H. Edwards, Krishna C. Balram, Stephanie A. Claussen, Rebecca K. Schaevitz, Emel Tasyurek, Yiwen Rong, Edward I. Fei, Theodore I. Kamins, James S. Harris, and David A. B. Miller, “Surface-Normal Ge/SiGe Asymmetric Fabry-Perot Optical Modulators Fabricated on Silicon Substrates,” J. Lightwave Technol. 31, 3995-4003 (2013)

[pa] J. E. Zucker, K.L. Jones, M.A. Newkirk, R.P. Gnall, B.I. Miller, M.G. Young, U. Koren, C.A. Burrus, and B. Tell, “Quantum well interferometric modulator monolithically integrated with 1.55 μm tunable distributed Bragg reflector laser,” Electron. Lett. Volume 28, Issue 20, 24 September 1992, 1888 – 1889 DOI:  10.1049/el:19921208

[pb] C. Rolland, R.S. Moore, F. Shepherd, and G. Hillier, “10 Gbit/s, 1.56 μm multiquantum well InP/InGaAsP Mach–Zehnder optical modulator,” Electron. Lett. Volume 29, Issue 5, 4 March 1993, p. 471 – 472  DOI:  10.1049/el:19930315

[pc] C. Lawetz, J.C. Cartledge, C. Rolland, and J. Yu, “Modulation characteristics of semiconductor Mach-Zehnder optical modulators,” J. Lightwave Technol. 15, 697-703 (1997) DOI: 10.1109/50.566692

[pd] R. A. Griffin, A. Tipper, and I. Betty, “Performance of MQW InP Mach-Zehnder Modulators for Advanced Modulation Formats,” in Optical Fiber Communication Conference and Exposition and The National Fiber Optic Engineers Conference, Technical Digest (CD) (Optical Society of America, 2005), paper OTuL5.

[pe] S. Corzine, P. Evans, M. Kato, G. He, M. Fisher, M. Raburn, A. Dentai, I. Lyubomirsky, A. Nilsson, J. Rahn, R. Nagarajan, C. Tsai, J. Stewart, D. Christini, M. Missey, V. Lal, H. Dinh, A. Chen, J. Thomson, W. Williams, P. Chavarkar, S. Nguyen, D. Lambert, S. Agashe, J. Rossi, P. Liu, J. Webjorn, T. Butrie, M. Reffle, R. Schneider, M. Ziari, C. Joyner, S. Grubb, F. Kish, and D. Welch, “10-Channel × 40Gb/s per channel DQPSK Monolithically Integrated InP-based Transmitter PIC,” in Optical Fiber Communication Conference/National Fiber Optic Engineers Conference, OSA Technical Digest (CD) (Optical Society of America, 2008), paper PDP18.

[pf] Gloria E. Hoefler, Yuchun Zhou, Maria Anagnosti, Ashish Bhardwaj, Payam Abolghasem, Adam James, Shawn Luna, Peter Debackere, Andrew Dentai, Thomas Vallaitis, Paul Liu, Mark Missey, Scott Corzine, Peter Evans, Vikrant Lal, Mehrdad Ziari, David Welch, Fred Kish, Joseph S. Suelzer, Preetpaul S. Devgan, and Nicholas G. Usechak, “Foundry Development of System-On-Chip InP-Based Photonic Integrated Circuits,”  IEEE Journal of Selected Topics in Quantum Electronics 25, 6100317 (2019) DOI: 10.1109/JSTQE.2019.2906270

T. H. Wood, C. A. Burrus, D. A. B. Miller, D. S. Chemla, T. C. Damen, A. C. Gossard and W. Wiegmann, “High-Speed Optical Modulation with GaAs/GaAlAs Quantum Wells in a p‑i‑n Diode Structure,” Appl. Phys. Lett. 44, 16‑18 (1984).

T. H. Wood, C. A. Burrus, D. A. B. Miller, D. S. Chemla, T. C. Damen, A. C. Gossard and W. Wiegmann, “131 ps Optical Modulation in Semiconductor Quantum Wells (MQW’s),” IEEE J. Quantum Electron. QE‑21, 117‑118 (1985)

T. H. Wood, C. A. Burrus, R. S. Tucker, J. S. Weiner, D. A. B. Miller, D. S. Chemla, T. C. Damen, A. C. Gossard and W. Wiegmann, “100 ps Waveguide Multiple Quantum Well (MQW) Optical Modulator with 10:1 On/Off Ratio,” Electronics Lett. 21, 693‑694 (1985)

D. S. Chemla, I. Bar-Joseph, C. Klingshirn, D. A. B. Miller, J. M. Kuo, and T. Y. Chang, “Optical Reading of Field-Effect Transistors by Phase-Space Absorption Quenching in a Single InGaAs Quantum Well Conducting Channel,” Appl. Phys. Lett. 50, 585‑587 (1987)

G. D. Boyd, D. A. B. Miller, D. S. Chemla, S. L. McCall, A. C. Gossard, and J. H. English, “Multiple Quantum Well Reflection Modulator,” Appl. Phys. Lett. 50, 1119‑1121 (1987)

I. Bar-Joseph, J. M. Kuo, C. Klingshirn, G. Livescu, D. A. B. Miller, T. Y. Chang and D. S. Chemla, “Absorption Spectroscopy of the Continuous Transition from Low to High Electron Density in a Single Modulation Doped InGaAs Quantum Well,” Phys. Rev. Lett. 59, 1357‑1360 (1987)

U. Koren, B. I. Miller, R. S. Tucker, G. Eisenstein, I. Bar-Joseph, D. A. B. Miller, and D. S. Chemla, “High-Frequency InGaAs/InP Multiple-Quantum-Well Buried-Mesa Electroabsorption Optical Modulator,” Electronics Letters 23, 621‑622 (1987)

D. S. Chemla, I. Bar-Joseph, J. M. Kuo, T. Y. Chang, C. Klingshirn, G. Livescu, and D. A. B. Miller, “Modulation of absorption in field-effect quantum well structures,” IEEE J. Quantum Electron. 24, 1664‑1676 (1988)

G. D. Boyd, J. E. Bowers, C. E. Soccolich, D. A. B. Miller, D. S. Chemla, L. M. F. Chirovsky, A. C. Gossard, and J. H. English, “5.5 GHz Multiple Quantum Well Reflection Modulator,” Electronics Lett. 25, 558-560 (1989)

K. W. Goossen, G. D. Boyd, J. E. Cunningham, W. Y. Jan, D. A. B. Miller, D. S. Chemla, and R. M. Lum, “GaAs‑AlGaAs Multiquantum Well Reflection Modulators Grown on GaAs and Silicon Substrates,” IEEE Photonics Tech. Lett. 1, 304‑306 (1989)

G. D. Boyd, J. A. Cavailles, L. M. F. Chirovsky, and D. A. B. Miller, “Wavelength dependence of saturation and thermal effects in multiple quantum well modulators,” Appl. Phys. Lett. 63, 1715‑1717 (1993)

K. W. Goossen, J. E. Cunningham, W. Y. Jan, and D. A. B. Miller, “Interleaved‑contact electroabsorption modulator using doping-selective electrodes with 25° C to 95° C operating range,” IEEE Photo. Tech. Lett. 5, 181‑183 (1993)

K. W. Goossen, J. A. Walker, L. A. D’Asaro, B. Tseng, R. Leibenguth, D. Kossives, 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 Photonics Technology Lett. 7, 360‑362, 1995

N. C. Helman, J. E. Roth, D. P. Bour, H. Altug, and D. A. B. Miller, “Misalignment-Tolerant Surface-Normal Low-Voltage Modulator for Optical Interconnects,” IEEE J. Selected Topics in Quantum Electronics, 11, 338 – 342 (2005)

J. E. Roth, O. Fidaner, R. K. Schaevitz, Y. -H. Kuo, T. I. Kamins, J. S. Harris, and D. A. B. Miller, “Optical modulator on silicon employing germanium quantum wells,” Opt. Express 15, 5851-5859 (2007)
http://www.opticsinfobase.org/abstract.cfm?URI=oe-15-9-5851

J. E. Roth, O. Fidaner, E. H. Edwards, R. K. Schaevitz, Y.-H. Kuo, N. C. Helman, T. I. Kamins, J. S. Harris, and D. A. B. Miller, “C-band side-entry Ge quantum-well electroabsorption modulator on SOI operating at 1 V swing,” Electronics Lett. 44, 49 – 50 (2008)

M. Jarrahi, T. H. Lee, and D. A. B. Miller, “Wideband, low driving voltage traveling-wave Mach-Zehnder modulator for RF photonics,” IEEE Photonics Technol. Lett. 20, 517-519 (2008)

D. A. B. Miller, R. K. Schaevitz, J. E. Roth, S. Ren, and O. Fidaner, “Ge Quantum Well Modulators on Si,” ECS Transactions, 16 (10) 851 – 856 (2008)

D. Englund, B. Ellis, E. Edwards, T. Sarmiento, J. S. Harris, D. A. B. Miller, and J. Vuckovic, “Electrically controlled modulation in a photonic crystal nanocavity,” Opt. Express 17, 15409-15419 (2009)

S. Ren, Y. Rong, T. I. Kamins, J. S. Harris, and D. A.B. Miller, “Selective epitaxial growth of Ge/Si_0.15Ge_0.85 quantum wells on Si substrate using reduced pressure chemical vapor deposition,” Appl. Phys. Lett. 98, 151108 (2011)

R. M. Audet, E. H. Edwards, P. Wahl, and D. A. B. Miller, “Investigation of limits to the optical performance of asymmetric Fabry-Perot electroabsorption modulators,” IEEE J. Quantum Electron. 48, 198 – 209 (2012) https://doi.org/10.1109/JQE.2011.2167960

R. K. Schaevitz, E. H. Edwards, J. E. Roth, E. T. Fei, Y. Rong, P. Wahl, T. I. Kamins, J. S. Harris, and D. A. B. Miller, “Simple Electroabsorption Calculator for Designing 1310nm and 1550nm Modulators Using Germanium Quantum Wells,” IEEE J. Quantum Electron. 48, 187 – 197 (2012)  https://doi.org/10.1109/JQE.2011.2170961

S. Ren, Y. Rong, S. A. Claussen, R. K. Schaevitz, T. I. Kamins, J. S. Harris, and D. A. B. Miller, “Ge/SiGe Quantum Well Waveguide Modulator Monolithically Integrated with SOI Waveguides,” IEEE Photonics Technol. Lett. 24, 461 – 463 (2012)  https://doi.org/10.1109/LPT.2011.2181496

E. H. Edwards, R. M. Audet, E. T. Fei, S. A. Claussen, R. K. Schaevitz, E. Tasyurek, Y. Rong, T. I. Kamins, J. S. Harris, and D. A. B. Miller, “Ge/SiGe asymmetric Fabry-Perot quantum well electroabsorption modulators,” Opt. Express 20, 29164-29173 (2012)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-20-28-29164

E. H. Edwards, L. Lever, E. T. Fei, T. I. Kamins, Z. Ikonic, J. S. Harris, R. W. Kelsall, and D. A. B. Miller, “Low-voltage broad-band electroabsorption from thin Ge/SiGe quantum wells epitaxially grown on silicon,” Opt. Express 21, 867-876 (2013)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-21-1-867

Ross M. Audet, Elizabeth H. Edwards, Krishna C. Balram, Stephanie A. Claussen, Rebecca K. Schaevitz, Emel Tasyurek, Yiwen Rong, Edward I. Fei, Theodore I. Kamins, James S. Harris, and David A. B. Miller, “Surface-Normal Ge/SiGe Asymmetric Fabry-Perot Optical Modulators Fabricated on Silicon Substrates,” J. Lightwave Technol. 31, 3995-4003 (2013)