I built a low-finesse confocal cavity with aluminum mirrors for use in the imaging of ultra-cold calcium ion plasmas. The confocal cavity provides stability at large mirror separations, a condition necessary for achieving both low finesse and narrow peak widths. Additionally, the finesse in the case of coherent input is effectively doubled compared to multi-mode resonance. The cavity was tested using a GaN diode laser input at 397nm. The transmission obtained indicated that the finesse of the cavity was slightly lower than the prediction based on measurements of the mirror reflectivities and the assumption of incoherent input.
I built a low-finesse confocal cavity with aluminum mirrors for use in the imaging of ultra-cold calcium ion plasmas. The confocal cavity provides stability at large mirror separations, a condition necessary for achieving both low finesse and narrow peak widths. Additionally, the finesse in the case of coherent input is effectively doubled compared to multi-mode resonance. The cavity was tested using a GaN diode laser input at 397nm. The transmission obtained indicated that the finesse of the cavity was slightly lower than the prediction based on measurements of the mirror reflectivities and the assumption of incoherent input.
The development of laser-machined, ultralow roughness micromirrors on optical fiber tips has enabled a new type of high-finesse Fiber Fabry-Perot cavities (FFPs). These microcavities are used very successfully in an increasing number of quantum technology applications, reaching from single-photon sources with various solid-state emitters to entanglement generation in ultracold atomic ensembles. They are also attractive for general photonics applications where high cavity finesse is desired, combinin narrow resonance width and large stopband with high transmission, excellent passive stability and built-in fiber coupling. I will give a short overview of this cavity technology and describe an experiment where we are using a next-generation FFP cavity to generate long-lived spin squeezed states in an atomic clock on a chip.
Fiber Fabry-Perot cavities, formed by micro-machined mirrors on the end-facets of optical fibers, are used in an increasing number of technical and scientific applications. Some of the most promising areas of application of these optical micro-resonators with high finesse and small mode volume are in the field of quantum communication and information. The resonator-enhanced light-matter interaction, for instance, provide basis for the realization of efficient optical interfaces between stationary matter-based quantum nodes and flying single-photon qubits. To date fiber Fabry-Perot cavities have been successfully applied in experiments interfacing single photons with a wide range of quantum systems, including cold atoms, ions and solid state emitters as well as quantum optomechanical experiments. Here we address some important practical questions that arise during the experimental implementation of high finesse fiber Fabry-Perot cavities: How can optimal fiber cavity alignment be achieved and how can the efficiency of coupling light from the optical fibers to the cavity mode and vice versa be characterized? How should optical fiber cavities be constructed and stabilized to fulfill their potential for miniaturization and integration into robust scientific and technological devices that can operate outside of dedicated laboratory environments in the future? The first two questions we answer with an analytic mode matching calculation that relates the alignment dependent fiber-to-cavity mode-matching efficiency to the easily measurable dip in the reflected light power at the cavity resonance. Our general analysis provides a simple recipe for the optimal alignment of fiber Fabry-Perot cavities and moreover for the first time explains the asymmetry in their reflective line shapes. The latter question we explore by investigating a novel, intrinsically rigid fiber cavity design that makes use of the high passive stability of a monolithic cavity spacer and employs thermal self-locking and external temperature tuning. The performance of this novel approach is compared to a more traditional, piezomechanically-actuated resonator that is feedback stabilized to a reference laser based on the Pound-Drever-Hall locking technique. Finally, with the application of single photon interfacing in mind we discuss the issue of fiber-generated background photons in Fiber Fabry-Perot cavities. We believe that, due to their simplicity, compactness and robustness, rigid fiber cavities could be a promising solution for miniaturized, integratable and scalable cavity quantum electrodynamic devices and further applications of FFPC with similar requirements.
Fiber Fabry–Perot cavities, formed by micro-machined mirrors on the end-facets of optical fibers, are used in an increasing number of technical and scientific applications, where they typically require precise stabilization of their optical resonances. Here, we study two different approaches to construct fiber Fabry–Perot resonators and stabilize their length for experiments in cavity quantum electrodynamics with neutral atoms. A piezo-mechanically actuated cavity with feedback based on the Pound–Drever–Hall locking technique is compared to a novel rigid cavity design that makes use of the high passive stability of a monolithic cavity spacer and employs thermal self-locking and external temperature tuning. Furthermore, we present a general analysis of the mode matching problem in fiber Fabry–Perot cavities, which explains the asymmetry in their reflective line shapes and has important implications for the optimal alignment of the fiber resonators. Finally, we discuss the issue of fiber-generated background photons. We expect that our results contribute toward the integration of high-finesse fiber Fabry–Perot cavities into compact and robust quantum-enabled devices in the future.
Abstract We present a self-assembled ultra-low expansion (ULE) cavity system designed for high-precision laser frequency stabilization. The cavity mirrors are bonded to the ULE spacer using a low thermal expansion adhesive, and the assembled cavity exhibits a finesse of nearly 3×104. A custom-designed multilayer aluminum housing was developed to passively isolate the cavity from environmental fluctuations. Long-term performance characterization reveals a frequency drift of approximately 164 kHz per day.After locking a diode laser to the cavity using the Pound-Drever-Hall technique, we achieve a linewidth of approximately 19.4kHz and a fractional frequency stability of6.4×10−13 at 1 s.To validate the reliability of this frequency-stabilized laser system, we applied it to Rydberg excitation spectroscopy via trap-loss measurements of cold 87Rb atoms. Compared to conventional wavelength meter locking, the cavity-stabilized system significantly improves spectral resolution, reducing the linewidth of the trap-loss spectrum from 34 MHz to 6 MHz. Our system offers a robust and cost-effective solution for high-resolution spectroscopy, with applications in coherent control of Rydberg atoms.
We characterize a high-finesse Fabry-Perot resonator for coupling with single neutral atoms. Our cavity consists of two mirrors with different reflectivities: One has minimal optical loss, and the other high transmission loss where more than 90% of the intracavity photons would be emitted. Cavity finesse, birefringent effects, and mechanical resonances are measured using the lasers at 780, 782, and 795 nm. In order to obtain cavity geometric parameters, we drive the adjacent longitudinal or transverse modes with two lasers simultaneously, and measure those frequencies using a precision wavelength meter (WLM). A major novelty of this method is that the parameters' uncertainty is solely determined by the resolution of the WLM, eliminating all of the temporal environment fluctuations. Moreover, the technique with two lasers consists of a vital approach for determining geometric parameters of a short cavity, with a free spectral range on the order of THz. Our system operates in the strong atom-cavity coupling regime that allows us to explore fundamental quantum optics and implement quantum network protocols.
Recent progress in atom optics has culminated in several demonstrations of atom interferometers. These rely on the passage of atoms through mechanical or light gratings and may be roughly characterized as Mach–Zehnder interferometers. In this communication, we propose a scheme to realize a Fabry–Perot interferometer for atoms. The mirrors are realized by the field gradient resulting from the spatial mode structure in optical or microwave cavities. When ultra- cold atoms impinge on such cavities, they experience quantum mechanical reflection and transmission that result in the appearance of longitudinal modes for the atomic wave function. We present a model of such a Fabry–Perot interferometer for two-level atoms. We discuss the intra-cavity matter–wave mode structure as well as the transmittivity and reflectivity characteristics of the interferometer. The potential generation of macroscopic quantum waves using such a device, as well as its potential as a sensitive photon detector, will be addressed.