Fabry-Perot Optical Cavity Research Articles

Radiation pressure induced oscillations of an optically levitating mirror

Optical Fabry–Perot cavity with a movable mirror is a paradigmatic optomechanical system. While usually the mirror is supported by a mechanical spring, it has been shown that it is possible to keep one of the mirrors in a stable equilibrium purely by optical levitation without any mechanical support. In this work, we expand previous studies of the nonlinear dynamics of such a system by demonstrating a possibility for mechanical parametric instability and the emergence of the “phonon laser” phenomenon.

Enhancement of the internal quantum efficiency in strongly coupled P3HT-C60 organic photovoltaic cells using Fabry-Perot cavities with varied cavity confinement.

The short exciton diffusion length in organic semiconductors results in a strong dependence of the conversion efficiency of organic photovoltaic (OPV) cells on the morphology of the donor-acceptor bulk-heterojunction blend. Strong light-matter coupling provides a way to circumvent this dependence by combining the favorable properties of light and matter via the formation of hybrid exciton-polaritons. By strongly coupling excitons in P3HT-C60 OPV cells to Fabry-Perot optical cavity modes, exciton-polaritons are formed with increased propagation lengths. We exploit these exciton-polaritons to enhance the internal quantum efficiency of the cells, determined from the external quantum efficiency and the absorptance. Additionally, we find a consistent decrease in the Urbach energy for the strongly coupled cells, which indicates the reduction of energetic disorder due to the delocalization of exciton-polaritons in the optical cavity.

Pixelated Filter Array for On-Chip Polarized Spectral Detection.

On-chip multi-dimensional detection systems integrating pixelated polarization and spectral filter arrays are the latest trend in optical detection instruments, showing broad application potential for diagnostic medical imaging and remote sensing. However, thin-film or microstructure-based filter arrays typically have a trade-off between the detection dimension, optical efficiency, and spectral resolution. Here, we demonstrate novel on-chip integrated polarization spectral detection filter arrays consisting of metasurfaces and multilayer films. The metasurfaces with two nanopillars in one supercell are designed to modulate the Jones matrix for polarization selection. The angle of diffraction of the metasurfaces and the optical Fabry-Perot (FP) cavities determine the spectrum's center wavelength. The polarization spectral filter arrays are placed on top of the CMOS sensor; each array corresponds to one pixel, resulting in high spectral resolution and optical efficiency in the selected polarization state. To verify the methodology, we designed nine-channel polarized spectral filter arrays in a wavelength range of 1350 nm to 1550 nm for transverse electric (TE) linear polarization. The array has a 10 nm balanced spectral resolution and average peak transmission efficiency of over 75%, which is maintained by utilizing lossless dielectric material. The proposed array can be fabricated using overlay e-beam lithography, and the process is CMOS-compatible. The proposed array enables broader applications of in situ on-chip polarization spectral detection with high efficiency and spectral resolution, as well as in vivo imaging systems.

Surface Modified Optical Fiber Fabry–Perot Cavity Pressure Sensor With Carbon Film

By the method of pulsed laser deposition of a Ni/C bilayer precursor films and annealing in air, amorphous carbon films were prepared on the surface of the capillary used for fabrication of optical fiber Fabry-Perot (FP) cavity pressure sensors. The surface morphologies of the coated and annealed carbon films were investigated through scanning electron microscopy. The images reveal that surface modification smoothes the irregular particles on the capillary surface and releases the stress induced by carbon and nickel deposition and oxy-hydrogen flame welding. Performance tests showed that the surface modified pressure sensors have good linearity for pressure response and the cavity length variations during the full cycle of pressure change is within 31 nm. Furthermore, thanks to the introduction of carbon films, the long-term stability of the cavity length can be kept within 10 nm during the tested 150 days.

Multicolor Bipolar Modulation of Titanium–Chromium Oxide Electrochromic Coatings

Electrochromic (EC) materials offer wide-ranging commercial applications, including smart windows, electrochromic mirrors, and programmable static displays. While many conventional electrochromic applications require the encapsulation of the EC materials and other components inside a sealed cell, there are cases where the color appearance of the object’s surface needs to be durable in atmospheric or aquatic environments. Among the current fabrication methods for EC materials, atomic layer deposition (ALD) remains less explored. In this work, we fill these gaps by employing ALD to grow a (Ti,Cr)Ox film as a new subset of EC coatings that operates in direct contact with aqueous solutions. The protective and bipolar coloration properties of the (Ti,Cr)Ox are achieved by the ALD alloying of TiO2 and CrOx nanocrystals. Intrinsic EC performance showed excellent cycle stability of more than 2000 cycles in aqueous electrolytes of high salinity and high corrosion resistance in pH = 0 acid. Furthermore, multicolor modulation has been achieved via a Fabry–Perot optical cavity design. Microstructural and spectroscopic characterizations combined with finite-difference time-domain (FDTD) modeling allow us to correlate the optical appearance with coating electronic and microstructures. This work showed that this ALD-grown ternary EC coating can also act as a surface protection layer and has unique advantages over other EC materials to achieve balanced performance among color tunability, coloration efficiency, and cycle stability.

Ultra-Sensitive Absorption-Based Gas Detecting Using Graphene-Covered Periodic Photonic Crystal Slabs Resonating Under Critical Coupling Condition at Mid-Infrared Frequencies.

In this paper, a novel chemical sensor is presented based on graphene deposited on the periodic pattern of the photonic crystal. The sensor structure is very simple to fabricate. Also, the proposed sensor thickness in the order of the nanometer makes it compact and suitable for integrating with optical equipment. The principle of sensing is based on the doping process of graphene due to the adsorption of the chemical molecules that serve as charge carriers. The sensor action under critical coupling results in generating the mid-infrared fano-resonance of the half-absorption band. Then, manipulating the graphene Fermi energy and geometrical parameters, a high quality factor can be attained in the resonance frequency that can provide the sensing possibility through the wavelength interrogation method. The results demonstrate that the proposed sensor can detect the chemicals with spectral shifts of 10 pm for steps of 5 charge carriers which is equal to a resolution smaller than 0.1ppm . Compared with other types of chemical graphene-based sensors employing optical fibers and plasmonic Fabry-Perot cavity, high resolution and sensitivity as well as the very simple geometry of the proposed sensing structure make it a promising candidate for ultra-sensitive chemical and biochemical detection.

Miniaturizing Ultrastable Electromagnetic Oscillators: Sub- 10−14 Frequency Instability from a Centimeter-Scale Fabry-Perot Cavity

The best performance from compact, portable, and repeatably manufactured electromagnetic (EM) oscillators has for decades been built upon crystalline quartz resonators operating at radio frequencies. Such a source of frequency-stable EM waves has enabled a wide range of applications of significant technical and societal benefit, such as navigation and communication systems, distributed sensing, geodesy, and fundamental physics. However, meeting demands for increased measurement sensitivity requires pushing beyond a fractional frequency stability of ${10}^{\ensuremath{-}13}$, typical of the best ovenized quartz. To date, such performance has been available in the microwave domain only with the use of complex cryogenic systems, or in the optical domain at the expense of larger volume and weight. In either case, the size, weight, and power of state-of-the-art EM oscillators has relegated their use to laboratory experiments. Here we demonstrate the validity of a manufacturable, compact Fabry-Perot reference that improves upon all other centimeter-scale oscillators by more than a factor of 10, including those based on solid-state optical resonators as well as quartz. In a specific implementation, we show an 8 ml bonded assembly containing three vacuum-gap Fabry-Perot optical cavities with mirrors lithographically fabricated on a single substrate, each with quality factor exceeding 10 billion. A laser stabilized to one of the cavities exhibits thermal-noise-limited phase noise for offset frequencies ranging from 1 Hz to nearly 1 kHz, and fractional frequency stability of $7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15}$ at 1 s. Our advance with lithographically defined and microfabricated mirrors is validated by rigorous models, which highlight a path to oscillators with size comparable to ovenized quartz, but with significantly improved performance. For example, we predict sub-${10}^{\ensuremath{-}14}$ performance is readily attainable with a Fabry-Perot cavity volume less than 2 ml.

High sensitivity tool for geophysical applications: a geometrically locked ring laser gyroscope.

We demonstrate that a middle sized ring laser gyroscope (RLG) can be a very sensitive and robust instrument for rotational seismology, even if it operates in a quite noisy environment. The RLG has a square cavity, 1.60×1.60m 2, and it lies in a plane orthogonal to the Earth's rotational axis. The Fabry-Perot optical cavities along the diagonals of the square were accessed, and their lengths were locked to a reference laser. Through a quite simple locking circuit, we were able to keep the sensor fully operative for 14days. We verified that the prototype properties are compatible with the seismic requirements. The obtained long term stability is of the order of 3nanorad/s, and the short term sensitivity is close to 2n a n o r a d/s⋅H z -1/2. These results are limited only by the noisy environment; our laboratory is located in a building downtown.

Characterization of mode field distribution in optical Fabry-Perot cavity based on nanofiber

The composite cavity optomechanical system combining optical Fabry-Perot (F-P) cavities, particles, and micro/nano mechanical oscillators is becoming more significant in the researches and applications of the fundamental physics, quantum information processing, and precision measurement. Characterizing the mode field distribution of optical F-P cavity is significant prior to the application of optical F-P cavity. In this paper, we propose and demonstrate a method to measure the waist of an optical F-P cavity and to characterize the mode field distribution of the optical F-P cavity by using a nanofiber nondestructively. In experiment, a nanofiber is placed in the mode of the optical F-P cavity with a fineness of around 1500. The optical F-P cavity is composed of two mirrors each with high reflectivity of 99.8%. The radius of curvature of the each mirror is 50 mm. The cavity length is (<inline-formula><tex-math id="M1">\begin{document}$ 80 \pm 4 $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="23-20221538_M1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="23-20221538_M1.png"/></alternatives></inline-formula>) mm. The nanofiber is fabricated from a single-mode fiber by the flame-brush method. The nanofiber diameter is around 440 nm. The transmission spectra of the optical F-P cavity are measured by scanning the cavity length. The free spectrum ranges and the inner cavity losses can be obtained from the transmission spectra. First, the influence of the nanofiber on the optical F-P cavity fineness is investigated. The fineness as a function of nanofiber position along the radial direction of the optical F-P cavity is measured. The fineness caused by the nanofiber decreases to a minimum value of about 240. Second, it is investigated that the optical F-P cavity inner loss caused by the nanofiber as a function of the nanofiber position along the radial direction of the optical F-P cavity when the nanofiber is placed at the waist of the optical F-P cavity. The inner loss of the optical F-P cavity caused by the nanofiber is related to the intensity distribution of the optical F-P cavity mode field, which is predicted theoretically. Thus, by making the Gaussian fitting of the optical F-P cavity inner loss as a function of the nanofiber position, we can obtain a waist radius of the optical F-P cavity to be (<inline-formula><tex-math id="M2">\begin{document}$ 72 \pm 1 $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="23-20221538_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="23-20221538_M2.png"/></alternatives></inline-formula>) μm. This is in good agreement with the theoretical calculation. Finally, the mode field distribution of the optical F-P cavity along the cavity axis is characterized. This method can be used for precisely controlling the coupling between the particles on the surface of nanofiber and optical F-P cavity. Besides, this method provides a good platform for studying the hybrid optomechanical system combining cavities, photons and quantum emitters.

Absolute distance measurement using cross correlation interferometer with a repetition rate multiplication frequency comb

In this paper, the Fabry-Perot etalon is used to multiply the repetition rate of the fiber optical frequency comb. The repetition rate is amplified from 250 MHz to 10 GHz, and the corresponding pulse interval is reduced from 1200 mm to 30 mm. For the pulse cross correlation ranging method, the repetition rate multiplication can greatly reduce the length requirement of the scanning reference arm. We analyze in detail the principle of cross correlation interferometry based on repetition rate multiplication frequency comb. A numerical mode of the function is comprehensively established. The basic parameters of optical source and Fabry-Perot cavity for the influence of filtered optical spectrum and cross correlation fringe are analyzed through the numerical simulation. The multiplied frequency comb is utilized for absolute ranging with the help of a pulse cross correlation method. By comparison, our result differs from the result obtained by a conventional counting interferometer only by 4 μm for distances up to 210 mm.

Phase-sensitive manipulation of squeezed vacuum via a dual-recycled Michelson interferometer.

The injection of squeezed vacuum state is an indispensable technology for the next generation gravitational wave observatory, which will open up a much larger window to the universe. After analyzing the absorption and dispersion properties of the reflected field of the dual-recycled Michelson interferometer (DRMI), we propose the phase-sensitive manipulation scheme of squeezed vacuum by utilizing the coupled-resonator-induced transparency in a dual-recycled Michelson interferometer (DRMI). In this way, the rotation frequency of squeezing ellipse can be finely tuned by the coupling strength, which overcome the limitation of the current solution (with a fixed rotation frequency) that employs a Fabry-Perot optical cavity as phase-sensitive manipulation element. This work will unleash the potential applications for quantum metrology beyond the shot noise limit.

Self-Assembled Biophotonic Lasing Network Driven by Amyloid Fibrils in Microcavities

Self-assembled biological structures have played a significant role in many living systems for its functionality and distinctiveness. Here, we experimentally demonstrate that the random dynamic behavior of strong light-matter interactions in complex biological structures can provide hidden information on optical coupling in a network. The concept of biophotonic lasing network is therefore introduced, where a self-assembled human amyloid fibril network was confined in a Fabry-Perot optical cavity. Distinctive lasing patterns were discovered from self-assembled amyloids with different structural dimensions (0D, 1D, 2D, and 3D) confined in a microcavity. Network laser emission exhibiting evidence of light coupling at different wavelengths and locations was spectrally resolved. Dynamic changes of lasing patterns can therefore be interpreted into a graph to reveal the optical correlation in biophotonic networks. Our findings indicate that each graph represents the highly unclonable features of a self-assembled network which can sensitively respond to environmental stimulus. This study offers the potential for studying dynamic biological networks through amplified interactions, shedding light on the development of biologically controlled photonic devices, biosensing, and information encryption.

Angle-independent plasmonic substrates for multi-mode vibrational strong coupling with molecular thin films

Vibrational strong coupling of molecules to optical cavities based on plasmonic resonances has been explored recently because plasmonic near-fields can provide strong coupling in sub-diffraction limited volumes. Such field localization maximizes coupling strength, which is crucial for modifying the vibrational response of molecules and, thereby, manipulating chemical reactions. Here, we demonstrate an angle-independent plasmonic nanodisk substrate that overcomes limitations of traditional Fabry-Pérot optical cavities because the design can strongly couple with all molecules on the surface of the substrate regardless of molecular orientation. We demonstrate that the plasmonic substrate provides strong coupling with the C=O vibrational stretch of deposited films of PMMA. We also show that the large linewidths of the plasmon resonance allow for simultaneous strong coupling to two, orthogonal water symmetric and asymmetric vibrational modes in a thin film of copper sulfate monohydrate deposited on the substrate surface. A three-coupled-oscillator model is developed to analyze the coupling strength of the plasmon resonance with these two water modes. With precise control over the nanodisk diameter, the plasmon resonance is tuned systematically through the modes, with the Rabi splitting from both modes varying as a function of the plasmon frequency and with strong coupling to both modes achieved simultaneously for a range of diameters. This work may aid further studies into manipulation of the ground-state chemical landscape of molecules by perturbing multiple vibrational modes simultaneously and increasing the coupling strength in sub-diffraction limited volumes.

Converting conventional electron accelerators to high peak brilliance Compton light sources

Several proposals have been put forward for converting electron accelerators to inverse Compton scattering (ICS) gamma sources. Typical approaches suggest combining near-IR solid-state lasers operating continuously at a multimegahertz repetition rate with e-beams when setting their interaction point inside a field-enhancement, Fabry-Perot optical cavity. We introduce here an alternative method of pairing particle accelerator beams with trains of long-wave-infrared, ${\ensuremath{\lambda}}_{L}\ensuremath{\approx}9--11\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ pulses from a picosecond ${\mathrm{CO}}_{2}$ laser of a novel architecture operating in a repetitive pulse-burst mode. Because of a considerable increase in the laser energy per pulse, combined with an order-of-magnitude higher number of laser photons per joule of laser energy, our approach allows us to increase the ICS peak flux and brilliance by 4 orders of magnitude compared to previous proposals while maintaining high (${10}^{11}--{10}^{12}\text{ }\text{ }\mathrm{ph}/\mathrm{s}$) average flux. This outcome is supported by the examples of the $\mathrm{DA}\mathrm{\ensuremath{\Phi}}\mathrm{NE}$ and CBETA accelerator facilities, where ${10}^{20}--{10}^{21}\text{ }\text{ }\mathrm{ph}/(\mathrm{s}\ifmmode\cdot\else\textperiodcentered\fi{}{\mathrm{mm}}^{2}\ifmmode\cdot\else\textperiodcentered\fi{}{\mathrm{mrad}}^{2}\ifmmode\cdot\else\textperiodcentered\fi{}0.1%BW)$ peak brilliances at 50--1000 keV photon energy range can be achieved and is comparable or exceeds the capabilities of contemporary synchrotron light sources at hard x rays. Such high-brightness ICS sources will find applications in pump-probe and other ultrafast studies that require building up meaningful datasets on a single x-ray pulse.

Low‐temperature‐grown gallium arsenide photoconductors with subpicosecond carrier lifetime and photoresponse reaching 25 mA/W under 1550 nm CW excitation

The authors show in this Letter that photoconductors based on GaAs grown at low temperatures can exhibit photoresponses as high as 25 mA/W under continuous-wave 1550-nm-wavelength illumination. It is achieved by using an optical Fabry–Perot cavity in order to improve the external quantum efficiency and by decreasing the post-growth annealing temperature down-to 450°C.

Enhanced optomechanical entanglement and cooling via dissipation engineering

We propose an optomechanical dissipation engineering scheme by introducing an ancillary mechanical mode with a large decay rate to control the density of states of the optical mode. The effective linewidth of the optical mode can be reduced or broadened, manifesting the dissipation engineering. To prove the ability of our scheme in improving the performances of the optomechanical system, we studied optomechanical entanglement and phonon cooling. It is demonstrated that the optomechanical entanglement overwhelmed by thermal phonon excitations could be restored via dissipation engineering. For the phonon cooling, an order of magnitude improvement could be achieved. Our scheme can be generalized to other systems with multiple bosonic modes, which is experimentally feasible with advances in materials and nanofabrication, including optical Fabry-Perot cavities, superconducting circuits, and nanobeam photonic crystals.

Pulsed entanglement and quantum steering in a three-mode electro-optomechanical system

We investigate bipartite entanglement and quantum steering in a three-mode, hybrid electro-optomechanical system consisting of a Fabry–Perot optical cavity, a nanomechanical oscillator and a lumped-element microwave cavity. The nanomechanical resonator is directly coupled to the optical cavity on the one side via the moving mirror of the Fabry–Perot cavity, and on the other side, it is capacitively coupled to the microwave cavity. There is no direct coupling between the cavity modes. The optical cavity is blue-detuned through excitation by a laser source emitting short pulses, while the microwave cavity is red-detuned through excitation by a voltage pulse generator. The presence of bipartite entanglement between different modes is verified based on the asymmetric entanglement criteria. Specifically, the system is shown to behave effectively as a two-mode system in which a perfect bipartite EPR state can be formed by the optical cavity and the mirror. The possibility of generating genuine tripartite entanglement is also investigated by examining the necessary conditions for multiparty multimode entanglement. Simultaneous coupling of the three modes is shown to be possible in accordance with the genuine tripartite entanglement criteria. Furthermore, we establish the existence of quantum steering between the modes using the steering parameter formality and examine the monogamy relations to quantify the amount of bipartite steering shared between different modes. Notably, steering is found to be present only between the mechanical and the optical cavity modes.

Mapping optical standing-waves of an open-access Fabry-Perot cavity with a tapered fiber.

We describe a method to map the standing-wave pattern inside an open-access Fabry-Perot optical cavity with sub-wavelength resolution by perturbing it with a commercially available tapered fiber. The method is applied to a fiber Fabry-Perot microcavity. We demonstrate its use in determining the relative position of the antinodes at two different wavelengths. In addition, we use the tapered optical fiber as a point-like source, allowing precise positioning of a microscope objective with respect to the cavity mode.

Effective factors in improving lasing performance in an atom-cavity system in the steady state regime

The behavior of a three-level atom in a V configuration with a multi-photon transition enclosed in a single-mode Fabry–Perot optical cavity is examined theoretically. To solve the describing equations of the atom-cavity system, a matrix continued fractions method has been used in the steady state. On the one hand, the effects of the number of transitions have been discussed over quantities involving population inversion, mean photon number and second-order correlation function. On the other hand, the changes of the coupling constant have been investigated on observables consisting atom-cavity correlation, the mean photon number and the second-order coherence function for different transitions. The influences of the number of transitions and the variations of the coupling constant are discussed separately on the improving lasing action in both cases. Finally, the transformation circumstances of the given three-level atom to an effective two-level one have been analyzed for various transitions. The results of the three-level atomic simulations appropriately confirm the correctness of several special conditions applied in the two-level atomic pattern.

Flexure-tuned membrane-at-the-edge optomechanical system.

We introduce a passively-aligned, flexure-tuned cavity optomechanical system in which a membrane is positioned microns from one end mirror of a Fabry-Perot optical cavity. By displacing the membrane through gentle flexure of its silicon supporting frame (i.e., to ∼80 m radius of curvature (ROC)), we gain access to the full range of available optomechanical couplings, finding also that the optical spectrum exhibits none of the abrupt discontinuities normally found in "membrane-in-the-middle" (MIM) systems. More aggressive flexure (3 m ROC) enables >15 μm membrane travel, milliradian tilt tuning, and a wavelength-scale (1.64 ± 0.78 μm) membrane-mirror separation. We also provide a complete set of analytical expressions for this system's leading-order dispersive and dissipative optomechanical couplings. Notably, this system can potentially generate orders of magnitude larger linear dissipative or quadratic dispersive strong coupling parameters than is possible with a MIM system. Additionally, it can generate the same purely quadratic dispersive coupling as a MIM system, but with significantly suppressed linear dissipative back-action (and force noise).