Self-forced stabilization of inter-modal oscillation in multi-section semiconductor lasers at X-band.

Forced oscillation based on self-injection locked phase-locked (SILPLL) opto-electronic oscillator (OEO) technique is the basis of highly stable and low phase noise oscillators to be used as a key component in modern communication and sensing systems. To avoid large-size modular OEO, inter-modal oscillation at X-band frequencies is achieved in a compact multi-mode multi-section semiconductor laser using InP foundry service. Self-forced oscillation technique of SILPLL is demonstrated, where a phase noise performance of -98 dBc/Hz is measured at 10 kHz offset carrier of 11 GHz, which is an improvement of 68 dB compared with the free-running condition, which corresponds with 600 times reduction in calculated timing jitters from the free-running case to reach 0.45 ps for over 1 kHz to 1 MHz bandwidth.

Cross-Spectrum PM Noise Measurement, Thermal Energy, and Metamaterial Filters.

Virtually all commercial instruments for the measurement of the oscillator PM noise make use of the cross-spectrum method (arXiv:1004.5539 [physics.ins-det], 2010). High sensitivity is achieved by correlation and averaging on two equal channels, which measure the same input, and reject the background of the instrument. We show that a systematic error is always present if the thermal energy of the input power splitter is not accounted for. Such error can result in noise underestimation up to a few decibels in the lowest-noise quartz oscillators, and in an invalid measurement in the case of cryogenic oscillators. As another alarming fact, the presence of metamaterial components in the oscillator results in unpredictable behavior and large errors, even in well controlled experimental conditions. We observed a spread of 40 dB in the phase noise spectra of an oscillator, just replacing the output filter.