Abstract
2.0x µm widely tunable external cavity lasers realized by combining a GaSb gain chip with a silicon photonics waveguide circuit for wavelength selection are demonstrated. Wavelength tuning over 58 nm from 2.01 to 2.07 µm is demonstrated. In the silicon photonic integrated circuit, laser feedback is realized by using a silicon Bragg grating and continuous tuning is realized by using two thermally tuned silicon microring resonators (MRRs) and a phase section. The uncooled laser has maximum output power of 7.5 mW and threshold current density of 0.8 kA/cm2. The effect of the coupling gap of the MRRs on tunable laser performance is experimentally assessed. A side mode suppression ratio better than 52 dB over the full tuning range and in the optimum operation point of more than 60 dB is achieved for the laser with weakly coupled MRRs.
Highlights
Tunable semiconductor lasers operating around 2 μm wavelength have attracted a lot of interest for molecular spectroscopy as CO2 and other atmospheric trace gases have strong and dense absorption lines in this wavelength range [1]
2.0x μm widely tunable external cavity lasers realized by combining a GaSb gain chip with a silicon photonics waveguide circuit for wavelength selection are demonstrated
Wavelength tuning over 58 nm from 2.01 to 2.07 μm is demonstrated
Summary
Tunable semiconductor lasers operating around 2 μm wavelength have attracted a lot of interest for molecular spectroscopy as CO2 and other atmospheric trace gases have strong and dense absorption lines in this wavelength range [1]. III-V-on-silicon widely tunable lasers fabricated with silicon photonics technology operating at 1.55 μm wavelength have been demonstrated in various ways, including the heterogeneous integration of III-V material on silicon through bonding technology and the butt coupling of a III-V gain chip to a silicon waveguide feedback circuit [16,17,18,19]. These widely tunable lasers were realized by using silicon microring resonators (MRRs) or sampled gratings as tunable filters. The measured side mode suppression ratio (SMSR) is higher than 52 dB over the full tuning range and in the optimum operation point more than 60 dB for the devices with weakly coupled MRRs
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