A record low-repetition rate from an on-chip monolithic InP extended cavity colliding-pulse mode-locked laser is experimentally reported. The device, fabricated in generic InP-based active-passive integration technology, makes use of integrated mirrors to enable its use as a building block within a photonic integrated circuit. This structure allows us to generate an electrical frequency comb with mode spacing of 1 GHz, determined by the 40.5 mm long resonator. Passive and hybrid mode-locking regime conditions are experimentally demonstrated. In the passive regime, an electrical beat tone at the fundamental repetition rate with an electrical linewidth (LW) of 398 kHz and a signal-to-noise ratio (SNR) >30 dB is measured. In the hybrid regime, the optical comb is locked to a continuous wave signal source, improving the LW of the generated signal and the SNR>40 dB.
We report the monolithic integration of a 15-channel multiplexer on indium phosphide. It covers the 7.1-to-8.5 µm wavelength range suitable for combining the outputs of several individual lasers. The fabrication is compatible with the growth of active layers, therefore enabling a fully integrate broadband laser source in the mid-infrared spectral range. Channels are accurately spaced in wavelength (97 nm) in good agreement with design.
In the mid-infrared (Mid-IR), arrays of distributed feedback Quantum Cascade Lasers (QCL) have been developed as a serious alternative to obtain extended wavelength operation range of laser-based gas sensing systems. In order to benefit from this extended wavelength range in a single output beam we have developed a platform for InP-based photonics. After the validation of all required building blocks, we are tackling the integration into a single monolithic device. We present the design, fabrication and performances of a tunable source, fully monolithic based on the echelle grating approach. The evanescent coupler has been designed to transfer all light adiabatically from the active region to a low loss passive waveguide, while taking advantage of the high gain available in the quantum wells. These results show the first realization of a monolithic widely tunable source in the Mid-IR and would therefore benefit to the development of fully integrated spectroscopic sensor systems.
We demonstrate and compare two different photonic-based signal sources for generating the carrier wave in a wireless communication link operating in the millimeter-wave range. The first signal source uses the optical heterodyne technique to generate a 113 GHz carrier wave frequency, while the second employs a different technique based on a pulsed mode-locked source with 100 GHz repetition rate frequency. The two optical sources were fabricated in a multi-project wafer run from an active/passive generic integration platform process using standardized building blocks, including multimode interference reflectors which allow us to define the structures on chip, without the need for cleaved facet mirrors. We highlight the superior performance of the mode-locked sources over an optical heterodyne technique. Error-free transmission was achieved in this experiment.
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