We experimentally study a fiber loop laser in a figure-8 configuration and explore the dependency of the degree of polarization on controlled parameters. To account for the experimental observations, a mapping is derived to evaluate the polarization time evolution. The nonlinearity induced by the Kerr effect and gain saturation gives rise to rich dynamics. We find that the degree of polarization can be increased by tuning the system into a region where the mapping has a locally stable fixed point.

We study optical detection of magnetic resonance of a ferrimagnetic sphere resonator, which is strongly coupled to a microwave loop gap resonator. Optical fibers are employed for coupling the sphere resonator with light in the telecom band. We find that magnetic resonance can be optically detected in the region of anti-crossing between the loop gap and the ferrimagnetic resonances. By measuring the response time of the optical detection we rule out the possibility that microwave induced heating is responsible for the optical detectability.

Coupling both optical light and microwave with magnetic materials is a pursued area of research recently as it will lead to emerging quantum technologies. Although spin waves in magnetic materials can be strongly coupled to microwave radiation, effective coupling of optical light with spin wave in magnetic system is still a major challenge.We have set up a figure-8 laser and integrated it with a coupled ferrimagnetic sphere-microwave resonator. We demonstrate the modulation of optical spectrum of figure-8 laser pulse by interaction with the microwave coupled ferrimagnetic YIG sphere. We observe that spectral peaks of optical pulses are governed by cavity modes formed by the YIG element.

We study nonlinear response of a ferrimagnetic sphere resonator (FSR) strongly coupled to a microwave loop gap resonator (LGR). The measured response in the regime of weak nonlinearity allows the extraction of the FSR Kerr coefficient and its cubic damping rate. We find that there is a certain range of driving parameters in which the system exhibits instability. In that range, self-sustained modulation of the reflected power off the system is generated. The instability is attributed to absorption-induced heating of the FSR above its Curie temperature.

Frequency mixing in ferrimagnetic resonators based on yttrium and calcium vanadium iron garnets (YIG and CVBIG) is employed for studying their nonlinear interactions. The ferrimagnetic Kittel mode is driven by applying a pump tone at a frequency close to resonance. We explore two nonlinear frequency mixing configurations. In the first one, mixing between a transverse pump tone and an added longitudinal weak signal is explored, and the experimental results are compared with the predictions of the Landau-Zener-Stuckelberg model. In the second one, intermodulation measurements are employed by mixing pump and signal tones both in the transverse direction for studying a bifurcation between a stable spiral and a stable node attractors. Our results are applicable for developing sensitive signal receivers with high gain for both the radio frequency and the microwave bands.

Optomechanical oscillators (OMOs) combine the co-existing high quality factor mechanical and optical resonances in an integrated device to realize low phase noise RF oscillations. While several attempts have been demonstrated towards modeling the phase noise in such oscillators, the close-to-carrier phase noise models in literature do not account for $1/f^3$ (pink noise) and higher order slopes in the phase noise spectra. Here we present a phase noise model, corroborated with experimental characterization of phase noise of two monolithic integrated silicon OMOs, accounting for contributions to the phase noise due to thermomechanical, and adsorption-desorption (AD) noise. The model shows good agreement with experimental data and provides further insights into the mechanisms underlying the noise processes contributing to different slopes in the phase noise spectra in OMOs.

Sensors based on the phenomena of Whispering Gallery Modes have the potential to detect analytes with high sensitivity. The design and optimization of Whispering Gallery Mode Resonator (WGMR) sensors in the THz regime can be modelled using computer simulations before fabrication and experimentation through Finite Element Analysis. We present modelling attempt and simulation results of a ring shaped WGMR along with the analyte molecule 'BSA'. These theoretical results can be used to study and obtain parameters to fabricate optimized devices which can yield results for sensing unlabeled analytes with low concentration and high specificity.

Whispering Gallery Mode Resonators represent a class of cavity devices with exceptional properties such as extremely small mode volume, very high power density, and very narrow spectral line width. Their importance for applications in very sensitive micro-sensors, have been recognized only in recent years. The sensitivity of this resonant technique has been found to be single molecular level, higher than that compared to most optical singlepass devices such as surface plasmon resonance biosensors. In this paper we present a brief review of the eld of WGM resonators, which includes the basic concept, the geometrical structures of resonators such as microdiscs, microtoroids and microspheres; the techniques for their fabrication and some of the most important applications as biosensors.

In this Letter, we experimentally demonstrate a terahertz (THz) whispering gallery mode (WGM) sensor based on a sapphire WGM resonator. The fundamental mode at 129.49 GHz with a Q-factor of 4.63×103 is used to study its sensitivity to adsorbed molecules. The efficiency of our sensor to detect rhodamine 6G dye molecules in a polyvinyl alcohol matrix at room temperature has been manifested, and a detection sensitivity of 25 parts per million has been achieved. Also, we report an analytical approach based on coupled-mode theory between the waveguide mode and the spherical resonator mode to evaluate the absorption coefficient of the adsorbed molecule on the resonator. The model is modified to evaluate optical constants of materials. The results obtained have been verified by continuous-wave THz transmission results. The results are of importance in sensing, metrology, and material characterization.