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In this Letter, we have studied the performance of a gallium nitride 370 nm Fabry–Perot laser diode self-injection locked via a high quality (Q-) factor magnesium fluoride whispering gallery mode (WGM) resonator and show that the state of locking strongly depends on frequency detuning between the internal laser cavity and the resonator modes. Optimizing the detuning, we were able to observe monochromatic laser emission with a sub-100 kHz linewidth. The Q-factor of the resonator measured in this regime exceeded 109.

We study crystalline fluoride microresonators for mid-infrared (mid-IR) applications. Whispering gallery mode resonators were fabricated with BaFsub2/sub, CaFsub2/sub, and MgFsub2/subcrystals. The quality factors were measured at wavelengths of 1.56 and 4.58 μm. The impacts of post-fabrication processing, impurities, and surface water are highlighted. The mid-IR optical losses due to multiphoton absorption are measured. It is found that MgFsub2/subresonators have a room temperature Q-factor of 8.3×10sup6/supat a wavelength of 4.58 μm, limited by multiphoton absorption.

International audience; Octave-spanning optical frequency combs are especially interesting in optical metrology owing to the ability of self-referencing. We report a theoretical study on the generation of octave-spanning combs in the whispering gallery modes of a microresonator. Through a modal expansion model simulation in a calcium fluoride microcavity, we show that a combination of suitable pump power, Kerr nonlinearity, and dispersion profile can lead to stable and robust octave-spanning optical frequency combs.

A low-threshold solid-state UV laser using a whispering gallery mode (WGM) resonator constructed from UV transparent crystalline material is demonstrated. Using a Ce3+:LiCaAlF6 resonator, we observe broad bandwidth lasing (280-330 nm) with a low threshold intensity of 7.5×10(9) W/m(2) and an effective slope efficiency of ~25%. The lasing time delay dynamics in the pulsed operation mode are also observed and analyzed. Additionally, a LiCaAlF(6) WGM resonator with Q=2×10(7) at 370 nm is realized. The combination of this high Q and the small WGM mode volume significantly lowers the pump power threshold compared to traditional cavity designs, opening the door for both tunable continuous-wave and mode-locked operation.

We propose a method for noncontact measurements of three-dimensional (3D) coordinates based on a Y-typed multiple-pinhole (MP) interferometer and demonstrate its feasibility in experiments. In this method, a Y-typed MP plate is inserted between the target and an image sensor to form a common-path interferometer. The 3D coordinates of the target are found by an effective algorithm using the discrete phase values on the measurement pinholes of the MP plate. These phase values can be directly extracted from a Fourier transform of the recorded intensity pattern without need of any iterative or phase-shifting algorithm. The method could be significant in real-time coordinate measurements and position tracking applications.

We demonstrate optical frequency combs using the fluorite whispering gallery mode resonator as a nonlinear Kerr medium. Two regimes of generation are observed, giving the record low repetition rate of 13 GHz, equal to the cavity's free spectral range (FSR) or high repetition rates of multiples of cavity FSR. An intermediate regime was also observed. Raman lasing spectrum similar to modulation instability in fibers was observed for the first time to the best of our knowledge.

We demonstrate efficient upconversion of sub-THz radiation into the optical domain in a high-Q whispering gallery mode resonator with quadratic optical nonlinearity. The 5x10^{-3} power conversion efficiency of continuous wave 100GHz signal is achieved with only 16 mW of optical pump., Comment: This revision is limited to discussion of only optical WGMs coupled with the external Rf field. Discussion of RF WGMs is now posted separately

A compact cold atom beam source based on a multistage two-dimensional magneto-optical trap (MOT) has been demonstrated and characterized. The multiple-stage design greatly reduces the overall size of the source apparatus while providing a high flux of atoms. The cold atom beam was used to load a separate MOT in ultrahigh vacuum, and we obtained an actual trap loading rate of 1.5 x 109 atoms/s while using only 20 mW of total laser power for the source. The entire source apparatus, including optics, can fit into a 4 cm x 4 cm x 13 cm volume.