We present a monolithic integrated low-threshold Raman silicon laser based on silicon-on-insulator (SOI) rib
waveguide ring cavity with an integrated p-i-n diode. The laser cavity consists of a race-track shaped ring resonator
connected to a straight bus waveguide via a directional coupler which couples both pump and signal light into and
out of the cavity. Reverse biasing the diode with 25V reduces the free carrier lifetime to below 1 ns, and stable,
single-mode, continuous-wave (CW) Raman lasing is achieved with threshold of 20mW, slope efficiency of 28%,
and output power of 50mW. With zero bias voltage, a lasing threshold of 26mW and laser output power >10mW can
be obtained. The laser emission has high spectral purity with a side-mode suppression of >80dB and laser linewidth
of <100 kHz. The laser wavelength can be tuned continuously over 25 GHz. To demonstrate the performance
capability of the laser for gas sensing application, we perform absorption spectroscopy on methane at 1687 nm using
the CW output of the silicon Raman laser. The measured rotationally-resolved direct absorption IR spectrum agrees
well with theoretical prediction. This ring laser architecture allows for on-chip integration with other silicon
photonics components to provide an integrated and scaleable monolithic device. By proper design of the ring cavity
and the directional coupler, it is possible to achieve higher order cascaded Raman lasing in silicon for extending
laser wavelengths from near IR to mid IR regions.
The strong optical nonlinearity of silicon and tight optical field confinement in silicon waveguides, accompanied by
silicon's unique material properties such as high optical damage threshold and thermal conductivity, enable compact
nonlinear photonic devices to be fabricated in silicon using cost effective CMOS compatible fabrication technology.
By integrating a p-i-n diode into the silicon waveguide, the nonlinear optical loss due to two photon absorption
induced free carrier absorption in silicon waveguides can be dramatically reduced, and efficient nonlinear optical
devices can be realized on silicon chips for high speed optical communications. In this paper, we report recent
development of silicon p-i-n waveguide based nonlinear photonic chips for wavelength conversion and dispersion
compensation applications. Wavelength conversion efficiency of -8.5 dB can be achieved in an 8-cm long p-i-n
silicon waveguide by four-wave mixing in continuous-wave operation, and chromatic dispersion compensation by
mid-span spectral inversion is demonstrated experimentally using silicon spectral inverter at the mid-span of a fiber
optical link, achieving transmission of optical data at 40 Gb/s over 320 km of standard fiber with negligible power
penalty. The unique advantages of using silicon over previously proposed nonlinear optical media for dispersion
compensation are discussed.
Recently, low threshold Raman silicon lasers based on ring resonator architecture have been demonstrated. One of the
key elements of the laser cavity is the directional coupler that couples both pump and signal light in and out of the ring
resonator from the bus waveguide. The coupling coefficients are crucial for achieving desired laser performance. In this
paper, we report design, fabrication, and characterization of tunable silicon ring resonators for Raman laser and amplifier
applications. By employing a tunable coupler, the coupling coefficients for both pump and signal wavelength can be
tailored to their optimal values after the fabrication, which significantly increases the processing tolerance and improves
the device performance.
We present a chip-scale ring resonator Raman silicon laser and amplifier based on a silicon-on-insulator rib
waveguide with an integrated p-i-n diode structure. The laser cavity consists of a race-track shaped ring resonator
connected to a straight bus waveguide via a directional coupler which couples both pump and signal laser light into
and out of the cavity. The optical propagation loss of the ring resonator is reduced to <0.3 dB/cm on average and the
effective free carrier lifetime in the waveguide can be shortened to <1 ns under reverse biasing, which efficiently
reduces the nonlinear loss due to two-photon absorption induced free carrier absorption. We achieve continuous-wave,
single-mode lasing with threshold of <20 mW and slope efficiency of >23%. Based on the same ring
resonator architecture, we build a compact, chip-scale Raman amplifier that takes advantage of the cavity
enhancement effect to lower the pump power and reduce the device size. We achieve over 3 dB amplification with 3
times less pump power in a 3 cm ring resonator compared to a straight waveguide of the same length. Our
experimental results agree with simulations. The ring resonator based laser and amplifier can be integrated on chip
with other silicon photonics components to provide a monolithic integrated photonic device.
We present a monolithic integrated Raman silicon laser and amplifier based on silicon-on-insulator rib waveguide race-track ring resonator with an integrated p-i-n diode structure. Under reverse biasing, we efficiently reduced the nonlinear loss due to two-photon absorption induced free carrier absorption and achieved continuous-wave net gain and stable, single-mode lasing with output power exceeding 30mW and 10% slope efficiency. The laser emission has high spectral purity with a side mode suppression exceeding 70dB and a laser linewidth of <100 kHz. This ring resonator architecture allows for on-chip integration with other silicon photonics components to provide a highly integrated and scaleable monolithic device. Using the ring resonator architecture, we can build a compact, chip scale Raman amplifier that takes advantage of the resonance effect to increase the effective pump power and reduce the device size. Our simulations suggest that a 3dB net gain can be achieved with 4dB less pump power in a 3cm ring compared to a straight waveguide of the same length.
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