Perot Etalon Research Articles

Photonic comb: a stabilized single-mode fiber etalon for wavelength calibration

We present a low-cost alternative to more complex laser metrology systems that uses a single-mode fiber Fabry–Perot etalon to generate an emission spectrum of evenly spaced lines with similar intensities, ideal for calibrating spectrographs (both in terms of wavelength and image quality). The system uses the hyperfine transition lines of 87Rb near 780.24 nm as an absolute reference. By controlling the cavity dimensions by small changes in temperature, we can tune and thus stabilize the transmission spectrum. A 20 Hz PID loop controls the etalon temperature and locks it to the 87Rb transitions. Through this method, we achieve a centroid error/precision of <1m/s (2.6 fm or 1.3 MHz) for 1 s integrations and 1 cm/s (0.026 fm or 13 kHz) for 30 min integrations of the reference line. We also show that a solution can be found to mathematically describe the spectrum. With the correct calibration and environmental controls in place, we show that this setup has the potential to be competitive with the best existing methods based on expensive and cumbersome laser combs.

LD-pumped all-solid-state single-longitudinal-mode Pr3+:LiYF4 laser at 915 nm

We report an InGaN laser diode (LD) pumped 915 nm single-longitudinal-mode (SLM) Pr3+:LiYF4 (Pr:YLF) laser for the first time. The all-solid-state 915 nm SLM laser is achieved by inserting two pieces of Fabry–Perot (F-P) etalons with different thicknesses in the resonant cavity. The maximum power of the SLM laser is ∼ 115 mW with the narrowest spectral linewidth of ∼ 110 MHz and the beam quality Mx2 and My2 factors are measured to be 1.16 (x) and 1.10 (y), respectively. In addition, we perform a theoretical simulation of combined F-P etalons transmittance. The experimental result is well-matched with the theoretical simulation. The first achievement of the 915 nm SLM Pr:YLF laser further expands the near-infrared laser applications.

Designing a sky-scanning Fabry–Perot interferometer system with a large size integrating sphere

Integrating spheres can be manufactured at sizes ranging from 1 mm to 3 m in diameter. It has been agreed widely by manufacturers that fitting a large-sized integrating sphere as per the customer requirement is a complex process. Thus, these spheres due to its large beam divergence from the exit port, have never been deployed for the calibration of aeronomy applications. In this article a optical system is described to integrate a large-sized integrating sphere with the Fabry–Perot etalon and thus devise a set-up to generate the concentric ring pattern and record it on the detector. The experimental set-up was verified by optical simulation using ZEMAX (OpticStudio) so as to validate the system’s performance in the laboratory. The important parameter finesse is calculated and its accuracy is found to be 80%.

Diode-Pumped Single-Longitudinal-Mode Pr3+:YLF Laser Based on Combined Fabry–Perot Etalons at 522.67 nm

We create a rate equation theoretical model of a continuous-wave end-pumped Pr3+:YLF SLM laser that characterizes the output properties of a single-longitudinal-mode (SLM) green laser. After inserting two Fabry–Perot (F–P) etalons with thicknesses of 0.3 mm and 0.5 mm and angles of 1.42° and 0.69° into the cavity, a single-longitudinal-mode green laser was generated. The maximum output power in single-longitudinal mode was 183 mW. The maximum absorbed pump power was 6.2 W. The corresponding linewidth is about 18 MHz. This work presents a simple method for generating a single-longitudinal-mode laser in the green spectral region, providing a practical approach for various green-laser-related applications.

Naked-eye observation of water-forming reaction on palladium etalon: transduction of gas-matter reaction into light-matter interaction

Palladium is the most prominent material in both scientific and industrial research on gas storage, purification, detection, and catalysis due to its unique properties as a catalyst and hydrogen absorber. Advancing the dynamic optical phenomena of palladium reacting with hydrogen, transduction of the gas-matter reaction into light-matter interaction is attempted to visualize the dynamic surface chemistry and reaction behaviors. The simple geometry of the metal-dielectric-metal structure, Fabry–Perot etalon, is employed for a colorimetric reactor, to display the catalytic reaction of the exposed gas via water-film/bubble formation at the dielectric/palladium interface. The adsorption/desorption behavior and catalytic reaction of hydrogen and oxygen on the palladium surface display highly repeatable and dramatic color changes based on two distinct water formation trends: the foggy effect by water bubbles and the whiteout effect by water film formation. Simulations and experiments demonstrate the robustness of the proposed Fabry–Perot etalon as an excellent platform for monitoring the opto-physical phenomena driven by heterogeneous catalysis.

A Model of Dual Fabry–Perot Etalon-Based External-Cavity Tunable Laser Using Finite-Difference Traveling-Wave Method

A physical model of an external-cavity tunable laser (ECTL) utilizing the vernier effect of a dual Fabry–Perot (FP) etalon is presented and simulated using the finite-difference traveling wave (FDTW) method. In this paper, we provide a detailed explanation of the physical principle and construction process of the model, as well as the simulation results for the laser. The model is precisely established by studying the time-dependent changes in the carrier concentration and optical field of different wavelengths inside the laser before reaching a steady state. By determining multiple parameters in the tuning region and gain region, the proposed model can calculate and predict various laser parameters, such as output power and side-mode suppression ratio (SMSR). Moreover, the FDTW method displays the change process of various parameters, such as carrier concentration and spectrum, in the convergence of various positions in the laser with femtosecond time resolution. This capability is promising for in-depth research on the inner mechanism of lasers.

Design and development of Fabry–Perot etalon based color filter using ebeam GLAD technique: Simulation and experiment

The design of Spatial Variable Color Filter (SVCF), based on the principle of Fabry–Perot (FP) etalon, has been analyzed in detail considering Ag as reflecting metallic layer and TiO2 as cavity layer. The effect of different thickness ranges of cavity layer for different order of interference peaks and the effect of varying thickness of reflecting layer has been investigated through simulation. A SVCF has been designed in the broad visible wavelength range of 464 to 670 nm based on the 2nd order interference peak of FP etalon for optimized spectral performance and it has been experimentally demonstrated using ebeam evaporation technique. The reflecting Ag layer has been deposited at normal angle and the tapered cavity layer of TiO2 has been deposited at 86° glancing angle. The distribution of thickness and dispersion relationship at various locations of the glancing angle deposited (GLAD) TiO2 thin films has been analyzed by spectroscopic ellipsometry measurements. The effect of lateral variation of dispersion properties of cavity layer caused by GLAD, on the spectral performance of the developed SVCF, has been investigated by both simulation and through spectral transmittance measurement. Overall results demonstrate the potential of the axial glancing angle deposition technique for the first time for development of SVCF in visible wavelength with high peak transmittance (∼67%) and a peak wavelength tunability of ∼4 nm/mm.

Drift Performance and Chromatic Thermal Response of a Temperature Stabilized Solid-etalon Calibrator

Etalon-based calibrators have rapidly gained popularity over the past decade in the field of high-precision radial velocity and high-resolution spectroscopy studies. Solid etalons are compact, pressure insensitive, commercially available alternatives to customized air spaced Fabry–Perot etalons. For tight-budget projects and weight-constricted missions, calibration system built from solid etalon is an interesting option to explore. For those, achievable spectral stability becomes the biggest question due to increased thermal sensitivity of the cavity material. Here, the design and performance of a low-cost solid-etalon calibrator is presented. A dual-loop temperature control system keeps the temperature fluctuations to within 1 mK rms when fully stabilized. Drift performance was tracked simultaneously with a laser frequency comb and the chromatic thermal response is measured through temperature tuning. The results indicate that a thermally controlled solid-etalon system can demonstrate sufficient short-term stability (<1 m s−1) for precise wavelength calibration in combination with a hollow-cathode lamp, and the measured drift and chromatic thermal response agree with theoretical predictions. Such systems are plausible candidates for cost-effective calibration of m s−1 level precision radial velocity instruments with improvement in thermal isolation, optimization in data processing, and long-term testing in the foreseeable future.

Fast dual-comb spectroscopy based on a dual-wavelength all-fiber ring laser with high repetition rate

We demonstrate fast dual-comb spectroscopy based on a high-repetition-rate dual-wavelength erbium-doped fiber laser with a large repetition rate difference. It can operate in three different dual-wavelength states with repetition rate differences of 4.32, 2.74 and 3.635 kHz, respectively. To the best of our knowledge, the corresponding refresh time can be as low as 231 μs, which is the fastest in dual-comb spectroscopy using a single fundamentally mode-locked all-fiber laser. The high repetition rate of approximately 154.68 MHz provides a maximum optical frequency bandwidth of 4.37 THz. Dual-comb spectroscopy was used to measure the transmittance curve of the Fabry–Perot etalon.

Design of Selective TPV Thermal Emitters Based on Bayesian Optimization Nesting Simulated Annealing

It is vital to further improve the design of TPV thermal emitters since the energy efficiency of thermophotovoltaic (TPV) systems is still not adequately high. In this paper, we propose a novel evaluator for the optimization of TPV thermal emitters, namely the percentage of effective figure (PEF) to replace the figure of merit (FOM). The associated algorithm, Bayesian optimization nesting simulated annealing (BOnSA), is developed to achieve better performance. By searching throughout the whole parameter space and then optimizing in a reduced space, BOnSA can lead to a satisfactory solution numerically for GaSb photovoltaic (PV) cells. When designing the emitter, the aperiodic material structure with an anti-reflection substructure and Fabry–Perot etalon is constructed from the material candidates. In particular, one of the optimal structures determined by BOnSA is {SiO2, ZnS, Ge, MgF2, W, Si, SiO2, W} with the value of PEF=0.822, which is better than the previous work by comparison. Moreover, by applying BOnSA to various structures, we have obtained higher values of PEF with less time cost, which thus verifies the efficiency and scalability of BOnSA. The results of our paper show that BOnSA provides an effective approach to the thickness optimization problem and that BOnSA is applicable in other relevant scenarios.

Double-pulse narrow-linewidth Pr:YLF laser with acousto-optic Q-switching and double Fabry–Perot etalon technology

According to the specificity of Pr:YLF crystal, this paper proposes the Q-switched double-pulse narrow-linewidth Pr:YLF laser output at 639 nm by combining the two-step acousto-optic Q-switching technology and the double Fabry–Perot etalon. And under the condition of repetition frequency of 10 kHz, the Q-switch was turned on twice in each pumping cycle, and the stable output of double-pulse narrow-linewidth laser with pulse interval of 40μs, pulse energy of 7.8 μJ and linewidth of 0.0418 nm was obtained. Meanwhile, we found that the laser can achieve the double-pulse single-longitudinal mode operation when the pulse energy was 2.3 μJ, and the corresponding spectral linewidth was 37.5 MHz.

Blue-pumped single-longitudinal-mode deep red band Pr: YLF Laser

This paper reports the single-longitudinal-mode (SLM) laser output of Pr: YLF at 721.2 nm by inserting double Fabry–Perot(F–P) etalons into the cavity. We use the correlation rate equation model to simulate the laser output characteristics and combine the results to design and conduct experimental research. By selecting the F–P etalon with appropriate thickness, when the maximum absorbed pump power is 2605 mW, this SLM solid-state laser achieved a maximum output power of 509 mW. The slope efficiency is 20.8%, and the optical–optical conversion efficiency is 19.5%. The emission spectrum has a linewidth of about 50 MHz. This study is the first time that Pr: YLF crystal has achieved single-frequency laser output in the band of deep red light by the double F–P etalons mode selection method. It lays a foundation for the broad application of SLM deep red laser.

Tunable laser frequency lock based on a temperature-dependent Fabry-Perot etalon.

A simple method for laser frequency stabilizing by a temperature-tuned Fabry-Perot etalon is reported. The etalon is a plano-convex lens that permits tuning the length and refractive index via controlling the temperature for shifting wavelengths in the region of 852 nm, with a transmission spectral linewidth of ∼72.5MHz and free spectral region of ∼16GHz. Using this scheme, arbitrary frequency locking of a laser with an adjustable frequency resolution of 2.34GHz/∘C is realized, and MHz-level long-term stability is demonstrated.

Thermally controlled optical resonator for vacuum squeezed states separation.

Future gravitational-wave detectors will use frequency-dependent squeezed vacuum states to obtain broadband reduction of quantum noise. Quantum noise is one of the major limitations to the sensitivity of these detectors. Advanced LIGO+, Advanced Virgo+, and KAGRA plan to generate frequency-dependent squeezed states by coupling a frequency-independent squeezed light state with a filter cavity. An alternative technique is under consideration, based on conditional squeezing with quantum entanglement: Einstein-Podolsky-Rosen (EPR) squeezing. In the EPR scheme, two vacuum entangled states, the signal field at ω0 and the idler field at ω0+Δ, must be spatially separated with an optical resonator and sent to two separate homodyne detectors. In this framework, we have designed and tested a solid Fabry-Perot etalon, to be used in an EPR table-top experiment prototype, thermally controlled without the use of a control probe optical beam. This device can also be used in optical experiments where the use of a bright beam to control an optical resonator is not possible, or where a simpler optical device is preferred.

Two-cavity dual-frequency Nd:YAG laser based on the principle of longitudinal mode selection by Fabry–Perot etalon

To obtain the dual-frequency laser output with large and tunable frequency difference, a design scheme of dual-frequency Nd:YAG laser with two standing-wave cavities sharing the common gain medium has been proposed, which is based on the principles of polarization splitting and single longitudinal mode selection of intracavity Fabry–Perot etalon. With each of the cavities containing a piece of Fabry–Perot etalon, the p- and s-polarized components of the laser at 1064 nm will be forced to oscillate simultaneously in single longitudinal mode in the linear and right-angle cavities, respectively. As a result, the orthogonally and linearly polarized dual-frequency laser at 1064 nm can be obtained. The principle of single longitudinal mode selection by use of the Fabry–Perot etalon has been analyzed, and the Fabry–Perot etalons have been designed. An experimental system of the two-cavity dual-frequency Nd:YAG laser at 1064 nm has been established, and the characteristics of single longitudinal mode oscillation of the two cavities have been investigated experimentally. The orthogonally and linearly polarized dual-frequency laser output at 1064 nm has been obtained; the main characteristics of the oscillating threshold and output power, the polarization state as well as the laser beam quality have been tested experimentally. The frequency difference of the dual-frequency laser has been tuned in turn to 16, 24, 37, and 76 GHz, by slightly adjusting the tilt angles of the intracavity Fabry–Perot etalons. Such a two-cavity dual-frequency Nd:YAG laser will be widely used in the synthetic-wave absolute-distance interferometry and other fields.

An Accelerometer Based on All Silica In-Line Fiber Fabry-Perot Etalon for High Temperature up to 800 °C.

High-temperature accelerometers have been widely used in aerospace, nuclear reactors, automobile technologies, etc. In this paper, a fiber-optic Fabry–Perot accelerometer (FOFPA) with a cantilever beam for high temperature is designed and experimentally demonstrated. The FOFPA is formed by bonding an all-silica in-line fiber Fabry–Perot etalon (ILFFPE) to one surface of the uniform cantilever beam with the lumped mass at the free end for acceleration measurement. The all silica in-line fiber FP etalon is made by welding two gold-coat single-mode fiber (GSMF) and a hollow silica glass tube (HST). The research results indicate that the sensitivity of the FOFPA is 0.02328rad/g, and the resonance frequency is 1146.6 Hz in the range of 1 g ~ 10 g. The high-temperature performance of the FOFPA was also evaluated. From 20 °C to 800 °C, the temperature drift is about 0.3178 nm/°C. The FOFPA has the potential of being applicable in higher temperatures compared to conventional accelerometers.

Integrated Fabry-Perot filter with wideband noise suppression for satellite-based daytime quantum key distribution.

Spectral filtering is essential in daytime quantum key distribution (QKD), which can suppress the strong background noise caused by scattered solar irradiation. An integrated Fabry-Perot filter is implemented based on a scheme that combines a Fabry-Perot etalon and a dense-wavelength-division-multiplex filter for narrow linewidth filtering and broad-spectrum noise suppression, respectively. This filter is integrated into a butterfly package with single-mode fibers for optical input and output, thereby enhancing high robustness and ease of use. The measurement results show that the filter has a linewidth of 25.6 pm, a noise suppression of over 44.7 dB ranging between 1380-1760 nm, an optical efficiency of 74.5% with variation less than 0.9% in 120 min, and a polarization fidelity after compensation exceeding 99.9%. The ability of fine-tuning the central wavelength with 9.5 pm/°C makes it very suitable for satellite-based applications under the Doppler effect. Further analysis is also given to demonstrate the prospects of applying this filter in future satellite-based daytime QKD applications.

A Narrow-Linewidth Optical Parametric Oscillator Inserted with Fabry–Perot Etalon

Nowadays, the Fabry–Perot etalon (F–P) has been widely utilized in the optical parametric oscillator (OPO) to improve the filtering performance. In this paper, we reported an F–P etalon composed of two ultra-thin silicon wafers spaced with the air. The linewidth of the signal laser and the threshold are 0.03 nm and 0.6 W, respectively when the proposed etalon is employed to a OPO system based on the MgO-doped LiNbO3 (MgO: PPLN). A stabilized output at 1492.4 nm is obtained, and a tunable, high-precision filtering performance can be achieved by varying the gap distance of the F–P etalon arbitrarily due to its ultra-thin thickness. In addition, the F–P etalon can work on a very wide bandwidth due to its weak absorption during the infrared and terahertz waveband. The high-precision tuning capability and wide-band function of proposed etalon may benefit many applications, including spectroscopy, filtering, and optical communication.

Multi-channel filter for UDWDM system designed based on stacking of Fabry-Perot etalons

The simulated multichannel comb filter [MCF] built on the stacking of the Fabry - Perot etalons that work in the telecommunication region between near-infra-red wavelengths (1538 −1558 nm) and (2333 - 2373 nm) has been demonstrated. Present work illustrates the dependence of defect modes produced on the stacked Fabry - Perot etalons. The FWHM of each channel is ∼0.043 picometers for the stacking of 20000 etalons. The spacing between the channels was ∼0.79 picometers and nearly uniform throughout the telecommunication band. The simulated MCF consists of ∼78 uniform channels within a range of ∼0.1 nm centered at 1550 nm.

Polymer-Stabilized Blue Phase and Its Application to a 1.5 µm Band Wavelength Selective Filter

The use of polymer-stabilized blue phase (PSBP) including a tolane-type liquid crystal was investigated to develop a voltage-controlled wavelength selective filter for wavelength-division-multiplexing optical fiber network. It was found that the tolane-type liquid crystal introduction can increase both a blue-phase temperature range and a Kerr coefficient. A Fabry–Perot etalon filled with PSBP functioned as a wavelength selective filter, as expected. The tuning wavelength range was 62 nm although peak transmission was not as high as expected. Numerical analysis suggested that light absorption in transparent electrodes may cause the issue. Minor change to the etalon structure will result in improved performance.