Fabry-Perot Optical Resonator Research Articles

A Differential Thermal Lens Spectrometry Method for Trace Detection.

Thermal lens spectroscopy (TLS) is a high-sensitivity method to determine the concentration of light-absorbing species in samples. Here, we implemented a transient configuration of the technique, with a focused pump and a collimated probe beam coaxially propagating. A Fabry-Perot optical resonator is incorporated allowing multi-passing of the probe beam through the sample to enhance sensitivity. We show how the low detection limit of the method can be reduced approximately by half by making differential measurements of the signal at a far field in the center point of the probe beam spot and that obtained by spatial filtering of the same beam, the so-called eclipsed signal. Measurements were performed in test samples of Deyman's organic dye, Strawberry 2143 v.7, dissolved in ethanol. The thermal lens signal measured as a function of the dye concentration in water at the center of the beam was compared with the differential signal resulting from this and the eclipsed beam.

Control of reactive collisions by quantum interference.

In this study, we achieved magnetic control of reactive scattering in an ultracold mixture of 23Na atoms and 23Na6Li molecules. In most molecular collisions, particles react or are lost near short range with unity probability, leading to the so-called universal rate. By contrast, the Na + NaLi system was shown to have only ~4% loss probability in a fully spin-polarized state. By controlling the phase of the scattering wave function via a Feshbach resonance, we modified the loss rate by more than a factor of 100, from far below to far above the universal limit. The results are explained in analogy with an optical Fabry-Perot resonator by interference of reflections at short and long range. Our work demonstrates quantum control of chemistry by magnetic fields with the full dynamic range predicted by our models.

Realignment-free cryogenic macroscopic optical cavity coupled to an optical fiber.

We present a cryogenic setup where an optical Fabry-Perot resonator is coupled to a single-mode optical fiber with coupling efficiency above 90% at mK temperatures without realignment during cooling down. The setup is prealigned at room temperature to compensate for the thermal contraction and change of the refractive index of the optical components during cooling down. The high coupling efficiency is achieved by keeping the setup rotation-symmetric around the optical axis. The majority of the setup components are made of Invar (FeNi36), which minimizes the thermal contraction. High coupling efficiency is essential in quantum optomechanical experiments.

Splitting of resonances in a curved optical fiber-based Fabry-Perot resonator

In this work, the splitting of resonance lines in a Fabry-Perot resonator formed by a section of a standard curved single-mode fiber with metal-coated ends is investigated numerically and experimentally. It is shown that this splitting is similar to the Autler-Townes splitting and results from a strong coupling between the fundamental mode of the core and the whispering gallery mode of the cladding of the curved fiber. The influence of all basic parameters of the curved resonator on the splitting of its resonance lines in the reflection and transmission spectra is considered. Prospects for the practical application of the effects studied for high-resolution optical refractometry, as well as the direction of further research are outlined.

Tests of Cryogenic Fabry–Perot Cavity with Mirrors on Different Substrates

Experiments were performed with Fabry–Perot optical resonators in vacuum at low temperatures. Mirrors were applied on substrates of various optical materials. An infrared laser with a wavelength of 1.064 microns was used. The pump power at the maximum could reach 450 mW. The evolution of the optical properties of the FP cavity was traced in the temperature range 300–10 K. The main parameters measured were the integral characteristics of the FP resonances–sharpness (finesse) and contrast of interference. Three types of substrates were tested: a sitall, an optical glass with ultra low thermal expansion (ULE); sapphire; and calcium fluoride. During cooling, the degradation of the integral characteristics of the FP cavity was observed for the sitall mirrors due to the loss of the properties of ULE, and for sapphire mirrors due to the birefringence effect. The satisfactory constancy of the integral characteristics of the FP resonator on calcium fluoride was demonstrated in the entire temperature range studied.

High sensitivity thermal lens microscopy: Cr-VI trace detection in water

In this work, a low detection limit for hexavalent chromium in water of parts per trillions (21ng/L) was achieved using a micro-spatial thermal lens spectroscopy setup with coaxial counter-propagating pump and probe laser beams and an integrated passive optical Fabry-Perot resonator, aided with a well-established diphenyl carbazide colorimetric method. Cr-VI concentrations in the range of μg/L, i.e. well-below the toxicity thresholds in humans and animals (26 and 190mg/L respectively) and below those delimited by international regulations for drink water (~0.05–0.5mg/L), have been obtained by measurements in bottled and tap water samples. The developed thermal lens microscope is also capable to detect Cr-VI directly in potassium dichromate solutions using pump beam wavelengths within the very low optical absorption region in the visible part of the spectrum, i.e., without the use of any colorimetric method.

-rays Factory

Gamma ray sources with high flux and spectral densities are the main requirements for new nuclear physics experiments to be performed in several worldwide laboratories with dedicated facilities. The paper is focalized on a proposal of experiment on $\gamma $ photons production using Compton collisions between the ${\rm DA}\Phi {\rm NE}$ electron beam and a high average power laser pulse, amplified in a Fabry-Perot optical resonator. The calculations show that the resulting $\gamma $ beam source has extremely interesting properties in terms of spectral density, energy spread and $\gamma $ flux comparable (and even better) with the last generation $\gamma $ sources. The energy of the $\gamma $ beam depends on the adopted laser wavelength and can be tuned changing the energy of the electron ring. In particular we have analyzed the case of a $\gamma $ factory tunable in the 2-9 MeV range. The main parameters of this new facility are presented and the perturbation on the transverse and longitudinal electron beam dynamics is discussed. A preliminary accelerator layout to allow experiments with the $\gamma $ beam is presented with a first design of the accelerator optics.

Fabry-Perot Vapor Microsensors Fabricated onto Fibre Endface by Multiphoton Polymerization Technique

We report on the fabrication of two different Fabry-Perot optical resonators on the endface of a SMF28 fibre, by employing Direct Laser Writing by multi-photon polymerization [1, 2]. We explore these endface fibre sensing probes for tracing common organic solvents [3]. The devices developed have been optimised for operation at the spectral region lying between 1415nm to1655nm, while being interrogated in reflection mode using a simple 50/50 fibre coupler. The laser used was a Ti:sapphire unit emitting at 800nm, 200fs pulses at a repetition rate of 50–80 MHz. The beam projection system was based on an inverse microscope; beam steering was performed using a x–y galvanometric mirror scanning the beam through a high magnification objective. Lateral resolution was of the order of 250nm [1]. The material that used for the fabrication of the endface microstructures is a zirconium-silicon, organic-inorganic hybrid photosensitive material [4]. The first microstructure consists of a thin, flat membrane suspended on four pillars attached onto the silica fibre endface (Fig. 1a). This architecture allows the formation of a small air cavity between the end face of the fibre and the suspended thin membrane, which acts as a multilayer Fabry-Perot resonator, providing interrogation capabilities of the media inside the air cavity section; or attached on the membrane endface [5]. Liquid or gaseous media can be trapped between the empty gap of the microdrum resonator, detecting refractive index or absorption changes in reflection mode. The specific cavity demonstrated herein consists of a 14.4um air gap formed between the fibre endface and the photopolymerised structure, while the membrane thickness is 10.4um , resulting in the periodic modulation of the reflected optical spectrum by notches of ~29dB in amplitude strength with a free spectral range of ~87nm.

Fabrication of glass micro-cavities for cavity quantum electrodynamics experiments

We report a process for fabricating high quality, defect-free spherical mirror templates suitable for developing high finesse optical Fabry-Perot resonators. The process utilizes the controlled re-flow of borosilicate glass and differential pressure to produce mirrors with 0.3 nm surface roughness. The dimensions of the mirrors are in the 0.5–5 mm range making them suitable candidates for integration with on-chip neutral atom and ion experiments where enhanced interaction between atoms and photons is required. Cavities constructed with these mirror templates are well suited to quantum information applications such as single photon sources and atom-photon entanglement.

Luminosity optimization schemes in Compton experiments based on Fabry-Perot optical resonators

The luminosity of Compton x-ray and $\ensuremath{\gamma}$ sources depends on the average current in electron bunches, the energy of the laser pulses, and the geometry of the particle bunch to laser pulse collisions. To obtain high power photon pulses, these can be stacked in a passive optical resonator (Fabry-Perot cavity) especially when a high average flux is required. But, in this case, owing to the presence of the optical cavity mirrors, the electron bunches have to collide at an angle with the laser pulses with a consequent luminosity decrease. In this article a crab-crossing scheme is proposed for Compton sources, based on a laser amplified in a Fabry-Perot resonator, to eliminate the luminosity losses given by the crossing angle, taking into account that in laser-electron collisions only the electron bunches can be tilted at the collision point. We report the analytical study on the crab-crossing scheme for Compton gamma sources. The analytical expression for the total yield of photons generated in Compton sources with the crab-crossing scheme of collision is derived. The optimal collision angle of the bunch was found to be equal to half of the collision angle. At this crabbing angle, the maximal yield of scattered off laser photons is attained thanks to the maximization, in the collision process, of the time spent by the laser pulse in the electron bunch. Estimations for some Compton source projects are presented. Furthermore, some schemes of the optical cavities configuration are analyzed and the luminosity calculated. As illustrated, the four-mirror two- or three-dimensional scheme is the most appropriate for Compton sources.

Piezoelectric Multimaterial Fibers

ABSTRACTHere we report on the design, fabrication, and characterization of fiber containing an internal crystalline non-centrosymmetric phase enabling piezoelectric functionality over extended fiber lengths [1]. A ferroelectric polymer layer of 30 μm thickness is spatially confined and electrically contacted by internal viscous electrodes and encapsulated in an insulating polymer cladding hundreds of microns in diameter. The structure is thermally drawn in its entirety from a macroscopic preform, yielding tens of meters of piezoelectric fiber. Electric fields in excess of 50V/μm are applied through the internal electrodes to the ferroelectric layer leading to effective poling of the structure. To unequivocally establish that the internal copolymer layer is macroscopically poled we adopt a two-step approach. First, we show that the internal piezoelectric modulation indeed translates to a motion of the fiber’s surface using a heterodyne optical vibrometer at kHz frequencies. Second, we proceed to an acoustic wave measurement at MHz frequencies: a water-immersion ultrasonic transducer is coupled to a fiber sample across a water tank, and frequency-domain characterizations are carried out using the fiber successively as an acoustic sensor and actuator. These measurements establish the broadband piezoelectric response and acoustic transduction capability of the fiber. The potential to modulate sophisticated optical devices is illustrated by constructing a single-fiber electricallydriven device containing a high-quality-factor Fabry-Perot optical resonator and a piezoelectric transducer.

Multimaterial piezoelectric fibres

Fibre materials span a broad range of applications ranging from simple textile yarns to complex modern fibre-optic communication systems. Throughout their history, a key premise has remained essentially unchanged: fibres are static devices, incapable of controllably changing their properties over a wide range of frequencies. A number of approaches to realizing time-dependent variations in fibres have emerged, including refractive index modulation, nonlinear optical mechanisms in silica glass fibres and electroactively modulated polymer fibres. These approaches have been limited primarily because of the inert nature of traditional glassy fibre materials. Here we report the composition of a phase internal to a composite fibre structure that is simultaneously crystalline and non-centrosymmetric. A ferroelectric polymer layer of 30 mum thickness is spatially confined and electrically contacted by internal viscous electrodes and encapsulated in an insulating polymer cladding hundreds of micrometres in diameter. The structure is thermally drawn in its entirety from a macroscopic preform, yielding tens of metres of piezoelectric fibre. The fibres show a piezoelectric response and acoustic transduction from kilohertz to megahertz frequencies. A single-fibre electrically driven device containing a high-quality-factor Fabry-Perot optical resonator and a piezoelectric transducer is fabricated and measured.

利用光纤法布里-珀罗谐振器干涉透射波长同时测量混合溶液中多溶质浓度

In order to simultaneously detect the multi-solute concentrations in mixed solution,system for measuring the multi-solute concentrations in mixed solution using optical Fiber Fabry-Perot Resonator(FFPR) is proposed.The relation between FFPR interference transmission wavelength and concentrations of the mixed solution is analyzed theoretically.The measuring system consists of an InGaAs LED,fiber coupler,FFPR sensor,opto-electrical convertor,amplifier and spectrometer.The analytical equation between concentrations and interference transmission wavelengths is standardized by measuring the samples contain ethanol and glycerin.The action script 2.0 is used as the programming language according to the mathematical relation.The real-time variation of the concentration change is monitored by the PC.

Thin polymer etalon arrays for high-resolution photoacoustic imaging.

Thin polymer etalons are demonstrated as high-frequency ultrasound sensors for three-dimensional (3-D) high-resolution photoacoustic imaging. The etalon, a Fabry-Perot optical resonator, consists of a thin polymer slab sandwiched between two gold layers. It is probed with a scanning continuous-wave (CW) laser for ultrasound array detection. Detection bandwidth of a 20-microm-diam array element exceeds 50 MHz, and the ultrasound sensitivity is comparable to polyvinylidene fluoride (PVDF) equivalents of similar size. In a typical photoacoustic imaging setup, a pulsed laser beam illuminates the imaging target, where optical energy is absorbed and acoustic waves are generated through the thermoelastic effect. An ultrasound detection array is formed by scanning the probing laser beam on the etalon surface in either a 1-D or a 2-D configuration, which produces 2-D or 3-D images, respectively. Axial and lateral resolutions have been demonstrated to be better than 20 microm. Detailed characterizations of the optical and acoustical properties of the etalon, as well as photoacoustic imaging results, suggest that thin polymer etalon arrays can be used as ultrasound detectors for 3-D high-resolution photoacoustic imaging applications.

Integrating cavity quantum electrodynamics and ultracold-atom chips with on-chip dielectric mirrors and temperature stabilization

We have fabricated an atom chip device which combines the circuitry for magnetic trapping of cold atoms with high-finesse optical resonators suitable for cavity QED in the single-atom strong coupling regime. Fabry–Perot optical resonators with finesse \(\mathcal{F}\ge2\times10^5\) were formed between a micropatterned on-chip planar mirror with lateral dimension of ≤ 100 μm and a curved mirror suspended above the chip. The strong and rapid thermal coupling between on-chip electrical and optical elements was utilized to stabilize the cavity mirror separation with servo bandwidth exceeding 100 kHz during simulated operation of the atom chip.

Cavity Nonlinear Optics at Low Photon Numbers from Collective Atomic Motion

We report on Kerr nonlinearity and dispersive optical bistability of a Fabry-Perot optical resonator due to the displacement of ultracold atoms trapped within. In the driven resonator, such collective motion is induced by optical forces acting upon up to 10(5) 87Rb atoms prepared in the lowest band of a one-dimensional intracavity optical lattice. The longevity of atomic motional coherence allows for strongly nonlinear optics at extremely low cavity photon numbers, as demonstrated by the observation of both branches of optical bistability at photon numbers below unity.

Atom Detection and Photon Production in a Scalable, Open, Optical Microcavity

A microfabricated Fabry-Perot optical resonator has been used for atom detection and photon production with less than 1 atom on average in the cavity mode. Our cavity design combines the intrinsic scalability of microfabrication processes with direct coupling of the cavity field to single-mode optical waveguides or fibers. The presence of the atom is seen through changes in both the intensity and the noise characteristics of probe light reflected from the cavity input mirror. An excitation laser passing transversely through the cavity triggers photon emission into the cavity mode and hence into the single-mode fiber. These are first steps toward building an optical microcavity network on an atom chip for applications in quantum information processing.

Tests of Relativity by Complementary Rotating Michelson-Morley Experiments

We report relativity tests based on data from two simultaneous Michelson-Morley experiments, spanning a period of more than 1 yr. Both were actively rotated on turntables. One (in Berlin, Germany) uses optical Fabry-Perot resonators made of fused silica; the other (in Perth, Australia) uses microwave whispering-gallery sapphire resonators. Within the standard model extension, we obtain simultaneous limits on Lorentz violation for electrons (5 coefficients) and photons (8) at levels down to 10(-16), improved by factors between 3 and 50 compared to previous work.

Characterization of scattering in an optical Fabry-Perot resonator

Roughness-induced scattering affects the performance of a resonator. We study the scattering of a single mirror first and compare the result with the losses of a two-mirror Fabry-Perot resonator. Besides some standard tools to characterize the losses, a new method based on the spectrally averaged transmission is introduced.

Ultra-Precise Measurement of Distance by Fabry-Perot Resonator

Length measurements in the region of nanometers by help of laser interferometers are influenced by the nonlinearity of their scale, which is usually ten or more nanometers. We developed and experimentally verified a new method, which has the resolution and linearity of the scale in the order of hundredth part of a nanometer. This method uses an optical Fabry-Perot resonator as a measuring element and by its help it is possible to measure small lengths and to test the nonlinearity of any interferometer with an uncertainty smaller than 0.1 nm The method takes advantage of a direct conversion of the relative changes of the optical path in measuring the arm of the Michelson interferometer to relative changes of the resonant optical frequency of the Fabry-Perot resonator. Frequency changes of the resonator resonance frequency have been monitored by a beat-frequency comparison between tunable He-Ne or semiconductor ECL (Extended Cavity Laser) laser and He-Ne-I2 optical frequency standard at 633 nm.