Silicon nitride (Si 3 N 4) has a higher nonlinear threshold compared to silicon, which reduces the effect of two-photon absorption. However, the low thermo-optic coefficient and the reduced refractive index contrast of thin Si 3 N 4 waveguides lead to a low thermal tuning speed and low thermal efficiency. This paper demonstrates a widely tunable III-V/Si 3 N 4 hybrid-integrated external cavity laser with a relatively faster switching time. The Si 3 N 4 external feedback circuit is based on 800-nm-thick Si 3 N 4 waveguides with an optical confinement factor of 87%. It allows the reduction of the oxide under-cladding layer thickness to 4 μm and the oxide upper-cladding layer to 1.7 μm without additional loss. The switching time between two non-adjacent lasing wavelengths is 60.7 μs. The maximum output power is 34 mW under 500 mA injection current. The side mode suppression ratio is more than 70 dB over the tuning range of 58.5 nm. The laser intrinsic linewidth is 2.5 kHz.
We present a hybrid dual-gain integrated external cavity laser with full C-band wavelength tunability. Two parallel reflective semiconductor optical amplifier gain channels are combined by a Y-branch in the Si3N4 photonic circuit to increase the optical gain. A Vernier ring filter is integrated in the Si3N4 photonic circuit to select a single longitudinal mode and meanwhile reduce the laser linewidth. The side-mode suppression ratio is ∼67 dB with a pump current of 75 mA. The linewidth of the unpackaged laser is 6.6 kHz under on-chip output power of 23.5 mW. The dual-gain operation of the laser gives higher output power and narrower linewidth compared to the single gain operation. It is promising for applications in optical communications and light detection and ranging systems.
We present a hybrid laser by using an InP reflective semiconductor optical amplifier chip butt-coupled with a SiN tunable reflector chip. The laser wavelength tuning range is 160 nm and the linewidth is 30 kHz.
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