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Description
Photonic integrated lasers in the near infrared and visible offer narrow linewidths in a compact form factor, enabling portable quantum sensing technologies with performances that match traditionally lab bound systems. The application of these chip lasers requires careful design and operation considerations to meet the strict wavelength, power and modulation performance parameters, which can be achieved through the integration of III-V semiconductor gain materials onto a low loss silicon nitride waveguide platform. This study investigates a master oscillator power amplifier (MOPA) design in this platform to produce pure frequency modulation on chip.
The approach utilizes injection current modulation into the III-V gain material to produce frequency modulation while simultaneously suppressing the residual amplitude modulation (RAM) that otherwise degrades the fidelity of precision metrology experiments. A method termed complex modulation synthesises an RF signal to counterbalance the detected RAM in phase and amplitude. This suppression signal is applied to the injection current of the integrated amplifier, cancelling the RAM whilst maintaining the frequency modulation produced by the laser.
Our results at modulation frequencies of 1 MHz and 10 MHz show suppression of RAM in the optical field down to 1 ppm and achieve a minimum fractional amplitude stability of $\text{σ}_\text{M}(\tau) \approx 3×10^{-6}$ for $\tau = 1-1000$ s. We demonstrate that RAM suppression is ultimately bound by the fundamental noise floor of the photodetector. This fully integrated solution to achieving pure frequency modulation on an established integrated photonic platform without introducing further electro-optical materials provides a simplified pathway for implementing these MOPA architectures in portable frequency modulation spectroscopy devices.
| I am the presenting author | Yes |
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