High-Power, Ultra-Low Noise Hybrid Lasers for Microwave Photonics and Optical Sensing

This paper describes the design, fabrication, and excellent performance achieved with prototype hybrid lasers incorporating a high performance gain chip coupled into a fiber external cavity including a novel fiber Bragg grating (FBG) reflector. Packaged ultra-low noise (ULN) hybrid lasers operating at 1550 nm and at 1319 nm with high output power, >100 mW, and extremely low relative intensity noise (RIN) are described. Devices provide extremely stable singlemode output with high side-mode suppression ratio (SMSR), typically above 70 dB, with worst case measured RIN at microwave frequencies (1-20 GHz) being below -165 dBc/Hz. Operation of these high power, low RIN devices within an analog optical link demonstrates a Spurious Free Dynamic Range as high as 114.6 dB.Hz
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. In addition to high power and very low RIN, the ULN hybrid lasers provide extremely small low frequency phase noise, with Lorentzian linewidths down to 15 Hz, enabling key Microwave Photonics and Optical Sensing applications. A comparison of the phase noise and Lorentzian linewidth of ULN lasers with different FBG designs / external cavity lengths is described, demonstrating the novel hybrid approach for achieving extremely low phase noise lasers.