GaAs/AlAs Multilayer Cavity with InAs Quantum Dots Embedded in Strain-Relaxed Barriers for Planar-Type Optical Kerr Gate Switches

Abstract

IntroductionUltrafast all-optical switches operating in the 1.55 µm waveband are among the most important devices in highbit-rate optical fiber communication systems. The planartype switches are especially attractive for dense parallel processing and simultaneous multichannel demultiplexing. Recently, we have proposed planar-type optical Kerr gate switches based on GaAs/AlAs multilayer cavity structures.[1] The strong internal light intensity due to the cavity effect yields drastic enhancement of nonlinear phase shift in the half-wave length (λ/2) cavity layer. Moreover, the optical Kerr signal intensity caused by the nonlinear phase shift can be further enhanced by using excellent nonlinear materials only in the λ/2 cavity layer. InAs quantum dots (QDs) in the 1.55 µm waveband are one of desirable nonlinear materials in the λ/2 cavity layer, since state filling in the QDs at low-excitation-power results in the large nonlinear refractive index change. [2,3] However, a slow decay (~ ns) of photogenerated carriers in the QDs is a crucial problem for the high-bit-rate operation because it leads to a strong dependence of response signal intensity on the pattern of pulse trains (pattern effect). In our recent study, self-assembled InAs QDs were successfully formed on strain-relaxed In 0.35 Ga 0.65 As barrier by molecular beam epitaxy (MBE).[4] The 20-layer stacked InAs QDs with strain-relaxed barriers showed optical absorption in the wavelength range of 1.35-1.65 µm. The fast carrier relaxation of 12-18 ps was demonstrated for the excitation wavelength of 1. 35-1.55 µm, [5] which comes from carrier relaxation into the nonradiative centers arising from the crystal defects related to the lattice-relaxation.In this paper, we report on successful fabrication of the GaAs/AlAs multilayer cavity structure with InAs QDs embedded in strain-relaxed barriers grown by MBE. Two InAs QD layers were inserted into the λ/2 cavity layer consisting of the strain-relaxed In 0.35 Al 0.65 As and In 0.35 Ga 0.65 As barriers. Decay of phtogenerated carriers in the QD-cavity sample was characterized by time-resolved transmission change measurement based on a pump-probe technique.

Optical Kerr signals of GaAs/AlAs multilayer cavities with two‐photon resonant quantum wells in the half‐wavelength layer

“…A thin cavity layer with large nonlinearity is sufficient to enhance the Kerr signal of the cavity structure, which is favorable for application of quantum dots, which are usually fabricated in a limited thin layer. We expect enhanced Kerr signals for a cavity with InAs quantum dots in the cavity layer, and the results will be presented elsewhere [11].…”

Marked reduction in photocarrier lifetime by erbium doping into self-assembled InAs quantum dots embedded in strain-relaxed InGaAs barriers

“…Recently, we have proposed planar-type optical Kerr gate switches based on GaAs/ AlAs multilayer cavity structures with InAs quantum dots (QDs) embedded in strain-relaxed barriers [6]. Strong optical Kerr signal from the QD-cavity structure was experimentally demonstrated [7,8] owing to the large optical nonlinearity of the InAs QDs and the enhanced nonlinear phase shift by cavity effects [9]. Excellent optical nonlinearities are provided by the QDs due to their delta-function-like density of states.…”

Time-Resolved Measurements of Sum-Frequency Generation Strongly Enhanced in (113)B GaAs/AlAs Coupled Multilayer Cavity

“…Optical microcavities consisting of GaAs/AlAs distributed Bragg reflector (DBR) multilayers are good candidates for nonlinear optical devices such as planar-type all-optical switches [1][2][3] because an extremely strong light field in the cavity layer markedly enhances nonlinear optical responses of the semiconductor material used in the cavity. Recently, we have proposed GaAs/AlAs coupled multilayer cavity structures for novel terahertz emission devices utilizing difference frequency generation (DFG) of two cavity modes.…”