We report a procedure to detect mid-infrared single photons at 4.65 m by means of a two-stage scheme based on sum-frequency generation, by using a periodically poled lithium niobate nonlinear crystal and a silicon avalanche photodiode. An experimental investigation shows that, in addition to a high timing resolution, this technique yields a detection sensitivity of 1.24 pW with 63 mW of net pump power.

Careful investigation of the reflectivity of two very high finesse integrated Fabry–Perot interferometers is reported. These two structures, made of GaAs active layer (1.7 μm thick) surrounded by two superlattice/AlAs Bragg reflectors, exhibit vertical cw lasing action at and above room temperature when photopumped with thresholds of 16 mW at 300 K and 56 mW at 380 K. Reflectivity measurements together with theoretical calculations show that layer regularity, accurate thickness control, and low interface roughness are key parameters for high-performance structures. Transmission electron microscopy on cleaved wedges and reflection electron microscopy are shown to be unique tools for measuring and characterizing these layers. Electron microscopy, optical reflection, and laser linewidth measurements are correlated and show that the layer flatness is dramatically increased by the introduction of six (2.5 Å) GaAs wells in the AlAs growth of the integrated dielectric reflectors. Reflectives of 97%, Fabry–Perot finesse as high as 100 (61 for direct measurements), and laser linewidths as small as 1.2 Å are reported.

No abstract

GaAs/AlGaAs quantum well and modulationdoped heterostructures grown by organometallic vapor phase epitaxy using trimethylamine alane Contribution of the bandfilling effect to the effective refractiveindex change in doubleheterostructure GaAs/AlGaAs phase modulators This work aims at a systematic study of phase modulation in GaAsl AIGaAs doubleheterostructure waveguides with different doping profiles. Both theoretical (part 1) and experimental (part II) aspects are investigated, leading to interesting new results. Phase modulation is the sum of a linear electro-optic term, a quadratic electro-optic term, and a freecarrier term. The carrier term is shown to be the sum of a plasma term, an intervalence-band term (for holes only), a band-filling term, and a band-shrinkage term, the latter being due to many-body effects. A new analytic expression for the band-filling term is derived which shows that the band-filling effect does not depend on the carrier effective mass. We prove that the band-shrinkage term is approximately half of the band-filling term, but has opposite sign. The phase modulation is computed using an overlap integral between the optical intensity and the local refractive-index difference. We also report an analytic expression for the modulation efficiency of a p-i-n junction double-heterostructure modulator. This expression is very accurate and only requires knowledge of the depletion width and the guiding parameters.6998

Phase modulation in GaAs/AlxGa1−xAs double heterostructures with different doping profiles is systematically investigated. Very good agreement between the experimental measurements and the theory developed in Part I of this paper is reported. By measuring the phase modulation for both transverse electric and transverse magnetic modes along the [110] and [11̄0] crystallographic directions, we are able to deduce accurate values for the linear electro-optic coefficient. Values of r41=−1.68×10−10 cm/V at λ=1.15 μm and r41=−1.72×10−10 at λ=1.09 μm are obtained with an estimated accuracy of ±5%. An accurate estimation of the carrier effect permits us to deduce the quadratic electro-optic coefficient for GaAs. The values are R11=−2.0×10−16 cm2/V2, R12=−1.7×10−16 cm2/V2 at λ=1.15 μm, and R11=−2.9×10−16 cm2/V2, R12=−2.4×10−16 cm2/V2 at λ=1.09 μm with an estimated uncertainty of ±25% for all values. Contrast measurement of Fabry–Perot fringes enables us to evaluate the modulator losses. A value of 4.8 cm−1 is reported for a P-n doped modulator (n=6×1017 cm−3). Free-carrier absorption is shown to be the dominant loss process in high-quality structures.