Fabrication And Characteristics Of High Speed InGaAs-GaAs Quantum-Wells Superluminescent Diode Emitting At 1053nm

Superluminescent diode(SLD) is a kind of device that the spontaneous emission experiences stimulated amplification over an extended path(single-pass gain amplification) and, possibly, one mirror reflection, but no feedback is provided. Thus, SLD has intermediate properties between the Light emitting diode(LED) and Laser diode(LD). Such as, wide spectral width, weak coherence, high power and high efficiency etc. A 1053 nm SLD as a seed source of inertial confinement fusion(ICF) system gives a good opportunity to get smaller size, higher stimulated Brillouin scattering(SBS) threshold, easier modulation and broad spectrum and peak wavelength output stabilized than the LD seeded laser. At the same time, it is not easily absorbed and dispersed by water, so, it also have been used for optical coherence tomography(OCT), optical sensing and measurement, and so on.InGa As/GaAs quantum well(QW) is used to be active layer of 1053 nm SLD. Due to the high mechanical strain in InGaAs QW layer on Ga As, the 2D growth of InGa As may change to 3D, which will lead to rapidly increase the defect number and degrade the SLD performance. And it is difficult to obtain a high modulation bandwidth, since the spontaneous emission dominate the SLD radiance. Its output spectrum is a Gaussian distribution, the peak output wavelength is very easy to be changed, and it will affect the quality of the optical signal. So, it is also need to study the stability of SLD spectrum.In this paper, the preparation of 1053 nm SLD based on high strained InGaAs/Ga As quantum well, high speed and stability of the output spectrum. The main contents include the device structure design, the optimization of growth contidions and the fabrication and packaging, etc. The high strained In0.34Ga0.66As/GaAs quantum well SLD module with ridged waveguide structure was fabricated, and the optical properties, spectrum stability, thermal performance and device reliability were analyzed. In the end, a 1053.7 nm In0.34Ga0.66As/Ga As double QW SLD with a-3 dB cutoff frequency of 1.7 GHz is obtained, corresponding to 6.5 mW output power.The main contents and results of this paper are as follows:1) The structure parameters of InxGa1-xAs/Ga As QW emitting at 1053 nm were computed, and the In composition is 0.34, the well width is 5.5 nm. Then, the waveguide layer(AlxGa1-xAs(x=0.2~0.5), 0.2 μm thickness) and confinement layer(Al0.5Ga0.5As, 1.3 μm thickness) were designed according to the influence of optical and carrier confinement, lattice, thermal resistance and electricity-optical efficiency.2) A SLD with 7 mW output power and less than 0.2 dB ripple was realized by the structure: ridge width 4 μm, residual thickness of confinement layer 0.1~0.3 μm, the active length is more than 405 μm, and a 400 μm length bent waveguide.3) The growth conditions of temperature, rate, interruption time and strained buffer layer were optimized to improve the quality of In0.34Ga0.66As/Ga As QW. The results were analyzed by XRD, PL, AFM, then the optimized growth conditions were achieved: 550 °C、8.33 ?/s and 3 s. The strained buffer layer In0.1Ga0.9 As can improve the quality of interface.4) The grown laser structure were processed into broad area(BA) laser diodes. The internal quantum efficiency and internal loss values are 75.8 % and 4.1 cm-1, respectively.5) SLDs with ridge waveguide were fabricated, the influence of active length, etched depth, area of p-side electrode and the doping concentration of n-AlGa As on the modulation bandwidth, output power and spectra were analyzed. In the end, a In0.34Ga0.66As/Ga As double QW ridge waveguide structure SLD with 4 μm width, 1.5 μm depth, and 700 μm active length was fabricated, a-3 dB cutoff frequency of 1.7 GHz is obtained at a DC bias current of l00 mA and 25 °C, corresponding to 2.5 mW output power from SMF with spectral modulation of less than 0.15 dB and spectral width of 24 nm.6) The stability of the spectra at different temperature and injection current were analyzed. The ripple shift with temperature, and the shift coefficients is-0.0048 nm/°C. The SLD was measured at continuous-wave(CW) and pulse(3 KHz,10 μs) conditions separately, and the wavelength shift coefficients are 0.35 nm/°C at CW condition and 0.36 nm/°C at pulse condition, respectively. The wavelength of the SLD shift with driver current insensitive to the temperature. In the end, the thermal impedance of the SLD is calculated to be 47.81 K/W. The reliability of the SLD module were investigated, After 800 hours of aging, neither sudden failures nor obvious degradation in the output power were observed, it shows very good reliability.