Design of multi-layer mirrors for measuring optical phase modulation at 1300 nm

A theoretical design and experimental realization of multi-layer mirrors for Fabry–Perot interferometry and optical telecommunications is described in this work. The mirrors were designed and fabricated by 13 successive thin layers to achieve very high reflectance at optical wavelengths around 1300 nm. Thin layers are ZnS and MgF₂ presenting high and low refractive index, respectively. Layer thickness λ_o/2 at λ_o=656 nm. Experimental results include characterization of transmittance of mirrors around 1300 nm. Additionally, the mirrors were integrated in a Fabry–Perot interferometer to characterize optical sources emitting at 1300 nm. Finally to show a practical application, optical phase modulation was analyzed, using the fabricated mirrors through a scanning Fabry–Perot interferometer acting as high-resolution optical spectrum analyzer (OSA).     

Mehrstrahlinterferenz und Eigenwellen im Parallelspiegel-Interferometer

Experiments with a Fabry Perot interferometer for microwaves (λ=3,2 cm) at oblique incidence show the importance of oscillation modes (well known from laser research) for the formation of multiple-beam interferences. A general formula is derived describing diffraction and multiple-beam interference in an interferometer with parallel mirrors of finite diameter. The formula is in quantitative agreement with the experimental results and includes as special cases the Fraunhofer diffraction at a slit and also the conventional multiple-beam interference (Fabry Perot rings).     

Optical rigidity in signal-recycled configurations of laser gravitational-wave detectors

We analyze laser gravitational-wave interferometers with additional mirror in signal port (signal-recycled configurations) which use the optical rigidity both for the Advanced LIGO (Fabry–Perot/Michelson) and GEO-600 (pure Michelson) topologies. We found a set of parameters to obtain better than Standard Quantum Limit (SQL) sensitivity without increasing laser pumping. The gain in sensitivity is inversely proportional to the bandwidth inside which this gain is achieved. By varying parameters one can change the shape of sensitivity curve from a single minimum curve to a double minimum curve through different regimes. This gives an additional possibility to increase the bandwidth but at the sacrifice of sensitivity. We also show that our “narrow band” regimes provide the gain in signal to noise ratio even for signals with wide spectrum.     

THz optical pulses from a coupled-cavity quantum-dot laser

Optical pulses are generated from a coupled-cavity quantum-dot (QD) laser consisting of a short QD-waveguide Fabry–Perot (F–P) cavity and three long external fiber Bragg grating (FBG) cavities. When the laser is biased at low operation current, the feedback from the external cavities dominates and laser pulses have a 1.01 THz repetition rate, determined by the equal frequency difference of the three FBGs. We are thus able to decouple the repetition rate of a mode-locked laser from the cavity length. With much higher bias current, the QD F–P cavity dominates and the repetition rate is switched to 43.8 GHz, defined by the length of the F–P cavity.     

Thermal noise computation in gravitational wave interferometers from first principles

We propose a universal method of computation of thermal noise in mirrors of gravitational wave interferometers based on first principles. We imagine a situation where a mirror is part of a Fabry–Perot cavity. The movement of the mirror's surface produces variation of the eigen frequency of the cavity, which is computed by evaluating the variation of the energy stored in cavity. We consider two particular examples: first, the thermal noise from a dielectric slab inside the Fabry–Perot cavity, and second, the polarization-dependent thermal noise in the folded cavity.     

Polarization and spectral characteristics of anisotropic ring laser cavities with nonideal mirrors

A mathematical model for calculating the polarization and spectral characteristics of eigenmodes of nonplanar ring optical cavities with allowance for the phase anisotropy of oblique-incidence mirrors is described. The results of the numerical modeling and experimental measurements of the characteristics of laser mirrors and mode spectra of practically important four-mirror cavities with a nonplanar symmetric axial contour are compared. It is shown that the proposed mathematical model can be applied to optimal selection of lasers for laser cavities with allowance for their real parameters.     

Optical feedback cavity ring-down technique for accurate measurement of ultra-high reflectivity

A novel cavity ring-down (CRD) technique, based on the optical feedback effect of Fabry–Perot diode lasers, is developed for accurate reflectivity measurement of highly reflective cavity mirrors. The strong optical feedback, including the direct reflection from the front cavity mirror of a linear ring-down cavity, is re-injected into the oscillator cavity of the diode laser, and large resonant peaks are observed in the ring-down cavity output signals. The diode laser is switched off by a threshold circuit when the amplitude of a resonant peak exceeds a pre-defined threshold. Exponentially decayed signals recorded immediately after switching off the laser are used to determine the cavity decay time. The ultra-high reflectivity of cavity mirrors is measured to be 99.99606% with a reproducibility of 0.00003%. Compared with the previous phase-shift CRD technique, the signal-to-noise ratio of the cavity output signals is improved with an enhancement factor of over 100.     

Systematical research on the characteristics of a vertical coupled Fabry–Perot plasmonic filter

A nanometric surface plasmon polariton (SPP) filter based on a vertical coupled metal–insulator–metal (MIM) Fabry–Perot resonator is proposed and analyzed. The transmission characteristics of the SPP filter are analyzed in detail by using the finite difference time domain method. And the resonance condition derived by the numerical method is consonant with the analytic model based on the Fabry–Perot model, which includes the metal loss and dispersion effects. And the simulation results show that multiple transmission dips can be formed and the resonance wavelengths of the transmission dips can be altered by the Fabry–Perot cavity length and width. Also the extinction ratio and the quality factor of the filter are affected by the barrier thickness of the coupling region. The proposed nanometric plasmonic filter is simple and very promising for the SPP waveguides platform.     

Fabry-Perot干涉仪的新应用

阐述了Ｆａｂｒｙ－Ｐｅｒｏｔ腔的工作原理以及在精细光谱结构研究、激光技术等领域的应用．结合作者的工作，给出了Ｆａｂｒｙ－Ｐｅｒｏｔ腔在微机械传感器和高速光电探测仪器研制这两个方面的新应用．     

An Extrinsic Fabry–Perot Optical Fiber Sensor Based on Nano-Magnetic Fluid

Abstract

An extrinsic Fabry–Perot optical fiber sensor based on nano-magnetic fluid and a Fabry–Perot interference is presented for magnetic field measurement. The sensing fiber end is coated with a thin film of SU-8 photoresist; immersing it into a nano-magnetic fluid forms a magnetic-field-dependent extrinsic Fabry–Perot interference. The relationship between the fringe contrast and magnetic field is analyzed in different concentrations of the magnetic fluid, and the concentration of 25% is most suitable for the measurement of the magnetic field intensity. The stability of the sensor is also addressed.     

Electromagnetically-Induced Transparency in Optomechanical Systems with Bose–Einstein Condensate

We study theoretically electromagnetically-induced transparency (EIT) in an optomechanical system that consists of a Bose–Einstein condensate (BEC) trapped inside a Fabry–Perot cavity driven by the laser field. The quantized laser field interacts with the collective density excitations (Bogoliubov mode) of the condensate. The phenomenon of electromagnetically-induced transparency is observed in the output of the probe laser field. We show that the probe laser field can efficiently be amplified or attenuated depending on the interaction of the BEC with the pump laser field. Furthermore, we explain the effect of atom–atom interaction on the transparency window and show that for increasing atom–atom interaction the transparency window increases.     

Numerical analysis of a swift, high resolution Generic Lightwave Integrated Chip wavelength monitor

A novel device capable of rapid and accurate wavelength determination in the C-Band of the telecommunications grid is presented. The device was developed with Planar Lightwave Circuit (PLC) technology, making it an ideal candidate for incorporation into next generation reconfigurable networks at add/drop sites that require stringent routing control. The described wavelength-meter can resolve any wavelength to a 2–5 pm precision within a sub-microsecond timeframe. The basic theory is outlined before the numerical aspects of the design and modelling are addressed. By establishing quadrature between two phase-shifted signals provided by two similar Fabry–Perot cavities, the interferometric throughput is referenced to a linear dielectric filter to resolve the wavelength in question. The elaborate mechanisms associated with multiple reflections in concatenated Fabry–Perot etalons warrant a meticulous verification by means of bidirectional beam propagation methods (BPM), discussed infra. Experimental characterisation verifies the theory. This signifies that concept of quadrature can also be applied in disciplines such as optical sensing and biophotonics. Thus, the device can be considered as a Generic Lightwave Integrated Chip (GLIC).     

Enhanced excess noise in laser cavities with tilted mirrors

Enhancement of the transverse excess-noise factor is theoretically predicted in optical laser cavities with tilted end mirrors and nonuniform transverse loss. In particular, it is shown that in a loss-guided laser close to the plane-plane geometric instability boundary the excess-noise factor that is induced by mirror tilting may largely exceed that predicted for the aligned cavity. This excess noise is related to beam walk-off induced by mirror tilting, which makes possible transient amplification of noise in the transverse plane.     

Micro-scale Fabry–Perot interferometer with high spectral resolution and tunable transmission frequency via chiral waveguide-emitter coupling

A micro-scale Fabry–Perot interferometer with high spectral resolution and tunable transmission frequency is proposed. In this scheme, two partially reflecting mirrors with a separation of several wavelengths is fabricated in a waveguide, and a two-level emitter is located between the mirrors and coupled to the waveguide with chiral interaction. We analytically show that the single emitter plays the role of a strongly dispersive medium and the full width at half maximum (FWHM) of the transmission fringes around the resonance frequency of the emitter can be narrowed by 5 orders of magnitude. The proposed micro-scale interferometer can have the same spectral resolution as meter-scale traditional interferometers. We also show that the central frequency of the narrowed transmission fringe can be tuned by adjusting the asymmetry of the emitter-waveguide coupling. Our scheme has potential applications in the fields of integrated optical circuit and quantum information processing.     

Displacement-noise-free gravitational-wave detection with two Fabry-Perot cavities

We propose two detuned Fabry-Perot cavities, each pumped through both the mirrors, positioned in line as a toy model of the gravitational-wave (GW) detector free from displacement noise of the test masses. It is demonstrated that the noise of cavity mirrors can be completely excluded in a proper linear combination of the cavities output signals. This model is illustrated by a simplified round trip model (without Fabry-Perot cavities). We show that in low-frequency region the obtained displacement-noise-free response signal is stronger than the one of the interferometer recently proposed by S. Kawamura and Y. Chen.     

Thermally induced dispersive optical bistability in silver nanosuspensions produced by pulsed laser ablation method

The thermally induced optical bistability in prepared silver (Ag) nanosuspensions have been studied experimentally, using Fabry–Perot and Mach–Zehnder interferometry methods. Two Ag nanosuspensions of different sizes were produced by different fluences of pulsed laser ablation method in distilled water. The pulsed Nd:YAG laser of 7 ns pulse width, 1064 nm wavelength and different fluences was employed to produce Ag nanosuspensions. Experimental observations were performed by an ultraviolet–visible–near infrared spectrophotometry. Structure and size of prepared Ag nanoparticles were diagnosed using transmission electron microscope images. Fabry–Perot and Mach–Zehnder interferometry methods were used to carry out the optical bistability process in prepared Ag nanosuspensions. In two considered interferometers, the obtained phase shifts of the hysteresis loops based on the optical bistability are inversely proportional to the nonlinear refractive index of samples and thickness of Ag nanosuspensions cells. Results indicate that the induced thermal effect of the optical bistability can be tuned by modifying parameters such as the nonlinear refractive index and applied interferometry methods. Hence, a desirable situation for the thermo-optical effects of the optical bistability can be easily realized in Ag nanosuspensions.     

Multilayer resonances sharpened by grating waveguide resonance

A multilayer planar structure comprising a highly reflective multilayer dielectric mirror and a corrugated waveguide is proposed for use as a narrow passband optical filter. The proposed filter has a much narrower linewidth than a usual Fabry–Perot cavity with two multilayer dielectric mirrors. It is shown that the narrowing of the linewidth is due to the strong spectral dependence of the phase of the wave reflected from the waveguide grating mirror. The shape of the pass band can be made symmetrical by a proper choice of the grating groove profile.     

Optical characteristics of a turbid medium between two mirrors

Using the one-dimensional Boltzmann equation, we examine the optical scattering properties of a turbid medium that is located between two mirrors with controllable reflectivity. We examine how the mirrors can be used to enhance the total transmission of an intensity modulated laser beam through this system. The analytical results show that, for certain modulation frequencies, the total transmission can be increased if the laser source is placed between the mirrors. This finding could improve diffusive imaging for those highly scattering media that are so thick that the laser light would not penetrate sufficiently deep in the absence of any mirrors.     

Ring and axis mode lasing in quasi-stadium laser diodes with concentric end mirrors

We fabricated quasi-stadium laser diodes whose resonators consist of two concentric curved end mirrors and two straight sidewall mirrors. We observed two lasing modes that correspond to different beam propagations along the cavity axis and along a ring trajectory, and different far-field patterns with wide angular separation. The modes can be selected by control of an electrode pattern. We also show that the far-field patterns numerically obtained by the extended Fox-Li mode calculation method are in good agreement with the experimental results.     

A high-finesse fiber optic Fabry–Perot interferometer based magnetic-field sensor

A high-finesse extrinsic Fabry–Perot interferometric sensor for the measurement of weak dc magnetic fields is demonstrated. The Fabry–Perot cavity is formed by aligning the fiber end-face and the TbDyFe rod end-face, and each end-face is coated by a mirror with a micro-lens. The length of the TbDyFe rod is changed by the variation of an applied dc magnetic field, leading a change of the Fabry–Perot cavity length. By interrogating the white-light interferometric spectrum, the wavelength of the resonant peak is tracked and the length of the Fabry–Perot cavity is obtained. The sensor exhibits a high sensitivity of 1510 nm/mT with a magnetic resolution of 25 nT.