InSb avalanche photodiodes on GaAs substrates for mid-infrared detection

We present indium antimonide-based devices for mid-infrared (mid-IR) detection with enhanced sensitivity. InSb devices will be useful for many applications, such as gas sensing and imaging. InSb avalanche photodiodes (APDs) monolithically integrated with GaAs substrates were fabricated with diameters ranging from 90 to $200~\mu \text{m}$ and extensively characterized at temperatures ranging from 77 K to 300 K. At 120 K a zero-bias responsivity of 2 A/W was measured, corresponding to a quantum efficiency of 55%. An experimental gain value of 10 at a reverse bias of −3 V was obtained at 120 K, which to the best of our knowledge, is the highest ever reported for InSb APDs. These results pave the way for the development of a monolithically integrated mid-IR array with added gain and wavelength tunability

Nonlinear properties of AlGaAs waveguides in continuous wave operation regime

Aluminum Gallium Arsenide (AlGaAs) is an attractive platform for the development of integrated optical circuits for all-optical signal processing thanks to its large nonlinear coefficients in the 1.55-μm telecommunication spectral region. In this paper we discuss the results of the nonlinear continuous-wave optical characterization of AlGaAs waveguides at a wavelength of 1.55 μm. We also report the highest value ever reported in the literature for the real part of the nonlinear coefficient in this material (Re(γ) ≈521 W<sup>−1</sup>m<sup>−1</sup>)

Fiber optics communications; (230.7405) Wavelength conversion devices; (130.3730) Lithium niobate

Abstract: We present the results of an in-depth experimental investigation about all-optical wavelength conversion of a 100-Gb/s polarization-multiplexed (POLMUX) signal. Each polarization channel is modulated at 25 Gbaud by differential quadrature phase-shift keying (DQPSK). The conversion is realized exploiting the high nonlinear χ ©2009 Optical Society of Americ

Highly nonlinear AlGaAs waveguides for broadband signal generation

In the last decade silicon on insulator-based waveguides have progressively attracted the attention of the nonlinear-optics research community. Due to the strong refractive index contrast of such waveguides and thanks to the very high nonlinear refractive index of silicon, strong nonlinear effects can be achieved in SOI structures, even at moderate pump power level (e.g. P < 1 mW) [1]. However, silicon also exhibits a very strong nonlinear absorption coefficient that severely limits the waveguide performance at power level above 1 mW. Very recently nonlinear AlGaAs waveguides were demonstrated, showing both efficient continuous wave and pulsed nonlinearities [2] with no two-photon absorption (TPA) effect, even at high power level

Study of the Gordon-Mollenauer Effect and of the Optical-Phase-Conjugation Compensation Method in Phase-Modulated Optical Communication Systems

Optical phase-modulated systems are promising candidates for the development of ultrahigh-bit-rate transmission links, thanks to their high spectral efficiency and increased tolerance to fiber-optic nonlinearities. However, their implementation was considerably slowed down by theoretical studies, suggesting that the transmission performance can be severely hindered by nonlinear phase noise (the so-called Gordon-Mollenauer effect). The simulations presented here show that, in realistic systems (including nonlinearity, dispersion, and attenuation), Gordon-Mollenauer noise does not represent the main source of signal distortions. We demonstrate that all nonlinear impairments can be efficiently compensated by optical phase conjugation, independent of system characteristics. The combination of optical-phase-conjugation with phase-modulation formats could enable ultrahigh-transmission-capacity and easy embedded-link upgrading

Experimental investigation on feedback insensitivity in semiconductor ring lasers

The insensitivity to optical feedback is experimentally measured for a semiconductor ring laser (SRL) and compared to that of a Fabry–Perot laser (FPL) fabricated with the same technology and on the same material. An analysis of the optical spectra reveals that the SRL remains nearly unaffected for values of optical feedback as strong as −23 dB. Furthermore, through both optical linewidth and self-mixing measurements, we show that the tolerance to feedback in SRLs is 25–30 dB stronger than in FPLs. This property makes SRLs very interesting candidates for the development of feedback-insensitive optical sources