Nonreciprocity in Photon Pair Correlations of Classically Reciprocal Systems.

Nonreciprocal optical systems have found many applications altering the linear transmission of light as a function of its propagation direction. Here, we consider a new class of nonreciprocity which appears in photon pair correlations and not in linear transmission. We experimentally demonstrate and theoretically verify this nonreciprocity in the second-order coherence functions of photon pairs produced by spontaneous four-wave mixing in a silicon microdisk. Reversal of the pump propagation direction can result in substantial extinction of the coherence functions without altering pump transmission.

Silicon carbide double-microdisk resonator.

We demonstrate the first silicon carbide (SiC) double-microdisk resonator (DMR). The device has a compact footprint with a radius of 24 µm and operates in the ITU high frequency range (3-30 MHz). We develop a multi-layer nanofabrication recipe that yields high optical quality (Q∼105) for the SiC DMR. Because of its strong optomechanical interaction, we observe the thermal-Brownian motions of mechanical modes in a SiC DMR directly at room temperature for the first time, to the best of our knowledge. The observed mechanical modes include fundamental/second-order common modes and fundamental differential (D1) modes. The D1 modes have high mechanical qualities >3800 at around 18.4 MHz tested in vacuum. We further show that optomechanical interactions, including linear and nonlinear optomechanical spring effects, can be observed in a SiC DMR at sub-milliwatt optical power. The SiC DMR has great potential for low-power optomechanical sensing applications in harsh environments.

Using a volume Bragg grating instead of a Faraday isolator in lasers incorporating stimulated Brillouin scattering wavefront reversal or beam cleanup.

A master-oscillator power-amplifier with stimulated Brillouin scattering (SBS) beam cleanup or wavefront reversal typically incorporates a Faraday isolator to outcouple the Stokes light, limiting the power scalability. Volume Bragg gratings (VBGs) have the potential for scaling to higher powers. We report here the results of tests on a VBG designed to resolve wavelengths 0.060 nm apart, corresponding to the 16 GHz frequency shift for SBS backscattering at 1064 nm in fused silica. Such an element may also find use in between stages of fiber amplifiers, for blocking the Stokes wave.