Large optical Kerr signal of GaAs/AlAs multilayer cavity with InAs quantum dots embedded in strain-relaxed barriers

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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.

Section: Introductionmentioning

confidence: 97%

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

Takahashi¹,

Mukai²,

Morita³

et al. 2010

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“…We have demonstrated optical Kerr gate switches based on a GaAs=AlAs multilayer cavity with InAs quantum dots (QDs) embedded in strain-relaxed barriers. [10][11][12][13][14][15] The strong internal light electric field due to the cavity effects markedly enhances of nonlinear phase shift in the halfwavelength (λ=2) cavity layer containing QDs. Vertical geometry all-optical switches based on the reflectance modulation of conventional InAs QDs placed in a GaAs= AlAs multilayer cavity have also been demonstrate by Jin and coworkers.…”

Section: Introductionmentioning

confidence: 99%

GaAs/AlAs triple-coupled cavity with InAs quantum dots for ultrafast wavelength conversion devices

Lu¹,

Ota²,

Kumagai³

et al. 2017

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We have investigated a GaAs/AlAs triple-coupled multilayer cavity structure with InAs quantum dots for an ultrafast wavelength conversion device. Three cavity modes with the resonance frequencies ω 1 , ω 2 , and ω 3 were used for efficient wavelength conversion via a four-wave mixing (FWM) process. Identical frequency separation between two adjacent modes (ω 1 % ω 2 = ω 2 % ω 3 ) was successfully realized using a controlled lateral thickness variation across the wafer. Time-resolved FWM signals from the triple-coupled multilayer cavity were measured using 100 fs laser pulses. The incident laser pulses were divided into two pulses and each of them was spectrally shaped individually so that the input and control pulses only covered the ω 1 and ω 2 modes, respectively. The wavelength-converted FWM signal with a frequency of ω 3 (= 2ω 2 % ω 1 ) was clearly observed when the sample was simultaneously irradiated with the input and control laser pulses.

“…We have demonstrated optical Kerr gate switches based on a GaAs/AlAs multilayer cavity with InAs quantum dots (QDs) embedded in strain-relaxed barriers. [10][11][12][13][14][15] The strong internal electric field of the cavity mode markedly enhances nonlinear phase shifts in the half-wavelength (/2) cavity layer containing QDs, which results in a strongly enhanced optical Kerr signal. 16) Vertical geometry all-optical switches based on the reflectance modulation of conventional InAs QDs placed in a GaAs/AlGaAs multilayer cavity have also been demonstrated by Jin and coworkers.…”

Section: Introductionmentioning

confidence: 99%

Four-wave mixing in a GaAs/AlAs triple-coupled multilayer cavity for novel ultrafast wavelength conversion devices

Kitada¹,

Yasunaga²,

Nakagawa³

et al. 2014

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Four-wave mixing (FWM) in a GaAs/AlAs triple-coupled multilayer cavity has been studied for novel planar wavelength conversion devices. Three half-wavelength cavity layers are connected in series using GaAs/AlAs distributed Bragg reflector multilayers to yield three cavity modes with equal frequency separation. Efficient and ultrafast wavelength conversion via nondegenerate FWM can be realized even in the normal incidence configuration because of the enhanced internal electric fields of the three cavity modes. The triple-coupled cavity sample was grown by molecular beam epitaxy and wavelength conversion was successfully demonstrated by measuring the spectrum of time-resolved FWM signals generated by spectrally shaped laser pulses. We found that precise control of the layer thickness is particularly important because the structural asymmetry due to the thickness inhomogeneity produces a nondegenerate FWM signal with low intensity. The temporal response was extremely fast and was almost limited by the photon lifetime (∼1 ps) of each cavity mode.