Measurement and analysis of optical gain spectra in 1.6 to 1.8 μm InAs/InP (100) quantum-dot amplifiers

Abstract

Small signal modal gain measurements have been performed on two-section ridge waveguide InAs/InP (100) quantum-dot amplifiers that we have fabricated with a peak gain wavelength around 1.70 µm. The amplifier structure is suitable for monolithic active-passive integration, and the wavelength region and wide gain bandwidth are of interest for integrated devices in biophotonic applications. A 65 nm blue shift of the peak wavelength in the gain spectrum has been observed with an increase in injection current density from 1,000 to 3,000 A/cm 2 . The quantum-dot amplifier gain spectra have been analyzed using a quantum-dot rate-equation model that considers only the carrier dynamics. The comparison between measured and simulated spectra shows that two effects in the quantum-dot material introduce this large blue shift in the gain spectrum. The first effect is the carrier concentration dependent state filling with carriers of the bound excited and ground states in the dots. The second effect is the decrease in carrier escape time from the dots to the wetting layer with decreasing dot size.

Dual-wavelength passive and hybrid mode-locking of 3, 45 and 10 GHz InAs/InP(100) quantum dot lasers

“…However one also expects then that such a structure would always be separate and stay separate. Another fact is that the measurement of optical gain of similar QD material [3] indicates that separation of GS and ES in our material is around 60nm, which is more than the 10-15nm wavelength distance observed in Fig. 4.…”

“…Progress in growth of InAs self assembled QDs [1] and quantum dashes [2] on InP substrate has allowed research on features of such quantum structures in the 1.5µm telecommunication window. At the COBRA Research Institute, optically active materials based on InAs QDs on n-type (100) InP substrate have been developed which provide peak gain in the wavelength range of 1.5µm to 1.8µm [3]. This brings the interesting properties of QDs to the wavelength region which is attractive not only for fiber optic communications but also for novel applications such as integrated tunable lasers for gas sensing and optical coherence tomography [4].…”

Small signal modal gain measurement of ridge waveguide semiconductor optical amplifiers operating at 2µm suitable for active-passive integration

“…The modal gain evaluations of SOAs we have fabricated is performed based on an implementation of a variable stripe length method [3]- [5]. Providing that there is no optical feedback and that no gain saturation occurs, the net modal gain g net () of a SOA can be related to its length L and amplified spontaneous emission (ASE) power P() with the following formula [4]:…”

“…The net modal gain can be further related to the material gain g: g net ()=g()- i , with  and  i being confinement factor and internal loss respectively, both taken to be wavelength independent within the range of interest. A nonlinear regression based fitting of the P sp () and g net () coefficients in relation (1) to experimental data recorded from a number of the SOAs with different lengths at each wavelength is used [5].…”

An InAs/InP(100) QD waveguide photodetector for OCT application

“…The QDSOA structure is realized in the COBRA active-passive optical integration schemes [2]. The average size of the InAs QDs is tuned to have emission wavelengths around 1700 nm [3].…”