Optical Ring Cavity Research Articles

Mode-locked Bloch oscillations in a ring cavity

We present a new technique for stabilizing and monitoring Bloch oscillations of ultracold atoms in an optical lattice under the action of a constant external force. In the proposed scheme, the atoms also interact with a unidirectionally pumped optical ring cavity whose one arm is collinear with the optical lattice. For weak collective coupling, Bloch oscillations dominate over the collective atomic recoil lasing instability and develop a synchronized regime in which the atoms periodically exchange momentum with the cavity field.

Label free detection of 5′hydroxymethylcytosine within CpG islands using optical sensors

Significant research has been invested in correlating genetic variations with different disease probabilities. Recently, it has become apparent that other DNA modifications, such as the addition of a methyl or hydroxymethyl group to cytosine, can also play a role. While these modifications do not change the sequence, they can negatively impact the function. Therefore, it is critical to be able to both read the genetic code and identify these modifications. Currently, the detection of hydroxymethylated cytosine (5′hmC) and the two closely related variants, cytosine (C) and 5′methylcytosine (5′mC), relies on a combination of nucleotide modification steps, followed by PCR and gene sequencing. However, this approach is not ideal because transcription errors which are inherent to the PCR process can be misinterpreted as fluctuations in the relative C:5′mC:5′hmC concentrations. As such, an alternative method which does not rely on PCR or nucleotide modification is desirable. One approach is based on label-free optical resonant cavity sensors. In the present work, toroidal resonant cavity sensors are functionalized with antibodies to enable label-free detection and discrimination between C, 5′mC, and 5′hmC in real-time without PCR. Specifically, epoxide chemistry is used to covalently attach the 5′hmC antibody to the surface of the cavity. Subsequently, to thoroughly characterize the sensor platform, detection of C, 5′mC, and 5′hmC is performed over a concentration range from pM to nM. At low (pM) concentrations, the hydroxymethylated cytosine produces a significantly larger signal than the structurally similar epigenetic markers; thus demonstrating the applicability of this platform.

Optical bistability and multistability in polaritonic materials doped with nanoparticles

We investigate the optical bistability and multistability in polaritonic materials doped with nanoparticles inside an optical ring cavity. It is found that the optical bistability and multistability can be easily controlled by adjusting the corresponding parameters of the system properly. The effect of the dipole–dipole interaction has also been included in the formulation, which leads to interesting phenomena. Our scheme opens up the possibility of controling the optical bistability and multistability in polaritonic materials doped with nanoparticles.

Detection of chemicals using a novel fiber-optic sensor element built in fiber loop ring-resonators

We developed an evanescent field access block (EAB) sensor with an etched single mode fiber, fabricated with a core diameter of 8μm and reduced cladding diameter down to 11μm by hydrofluoric acid (HF) etching technique. Here, we describe the manufacturing process of the packaged sensor block and demonstrate that the sensor is able to detect sample absorption and refractive index (RI) changes. The sensor is tested with different chemical solutions such as ethylenediamine (EDA), dimethyl sulfoxide (DMSO) and ethanol (C2H5OH).At the same time, we fabricated (at CSIR-CGCRI) high quality optical fiber couplers having low splitting ratios (99.5:0.5%), which we used to build a 4m long optical evanescent-wave fiber ring cavity with an embedded EAB. After a careful analysis of the fiber loop characteristics, we performed cavity ring-down measurements in order to detect the presence of liquid samples on the EAB.

Analysis of frequency noise in ultra-stable optical oscillators with active control of residual amplitude modulation

Two 1,064-nm Nd:YAG lasers frequency stabilized by high-finesse optical cavities are developed to investigate various noise mechanisms in ultra-stable optical oscillators. Active control of residual amplitude modulation using a separate sensing path is implemented and its effectiveness in the presence of a resonant optical cavity is theoretically analyzed and experimentally verified by measuring the rejection ratios in optical heterodyne beat between a perturbed laser and a stable reference. Laser frequency noises originated from vibration, residual amplitude modulation, quantum-limited shot noise, and electronic noise are experimentally analyzed. With active control, residual amplitude modulation is suppressed to below 1 x 10(-6) at 0.02-1,000 s, reaching a minimum of 2 x 10(-7) at similar to 2 s. A frequency stability of 2 x 10(-15) is obtained from 0.1 to 10 s, and the optical heterodyne beat of the two Nd: YAG lasers shows 1-Hz linewidth with a measurement time of 4.096 s. In addition, the experimentally determined linewidths agree well with the calculation according to a simplified relationship between the linewidth and the underlying flicker noise that modulates the laser frequency.

Stable Scanning of Dressing Fields on Multiwave Mixing in Optical Ring Cavity

We investigate a novel detection technique to study the coherent control of dressed multiwave mixing (MWM) process. A stable laser dressing field with a wavelength of 480 nm is realized via the second harmonic generation technique. By scanning such dressing field, stable Rydberg MWM signals with high signal-to-noise ratio are observed. With the MWM signals oscillated in a stabilized three-mirror cavity and cavity dressing field scanned, dressed MWM cavity modes are obtained. Thanks to the stable 480 nm and cavity dressing fields, the long-term drift of dressed MWM in cavity can be dramatically reduced to <4 MHz from 100 MHz.

Simple method of optical ring cavity design and its applications.

When an optical ring cavity is designed, the beam radii at some special positions, especially at the beam waists are very interested in, since the gain mediums, nonlinear crystals and others important optical elements are generally located at the beam waist. In this paper, we firstly presented a simple method for designing optical ring cavities based on the self-consistency theory and the fact that q parameter is uniquely determined by the waist beam radius and its position. This approach is different from ABCD method and it no longer requires cumbersome calculation. The calculations of designing optical ring cavities are simplified because q parameter only has imaginary part at beam waist plane. Moreover, designing the resonant cavity through the calculation of beam waist radii and their position has great practical significance, because it is very easy to adjust the waist radii and the positions at the important optical elements. We employed this method to design an end-pumped six-mirror ring cavity continuous-wave passively mode locked laser. The experiment of a highly stabilized continuous-wave mode locked (CWML) laser was investigated and the results coincided with the theoretical studies very well. The investigation results show that the simple method can be used to design optical ring cavities conveniently, intuitively and efficiently.

Ultrasensitive nanomechanical mass sensor using hybrid opto-electromechanical systems

Nanomechanical resonators provide an unparalleled mass sensitivity sufficient to detect single biomolecules, viruses and nanoparticles. In this work we propose a scheme for mass sensing based on the hybrid opto-electromechanical system, where a mechanical resonator is coupled to an optical cavity and a microwave cavity simultaneously. When the two cavities are driven by two pump fields with proper frequencies and powers, a weak probe field is used to scan across the optical cavity resonance frequency. The mass of a single baculovirus landing onto the surface of the mechanical resonator can be measured by tracking the resonance frequency shift in the probe transmission spectrum before and after the deposition. We also propose a nonlinear mass sensor based on the measurement of the four-wave mixing (FWM) spectrum, which can be used to weigh a single 20-nm-diameter gold nanoparticle with sub-femtogram resolution.

Length control of an optical resonator using second-order transverse modes.

We present the analysis of an unorthodox technique for locking a laser to a resonant optical cavity. Error signals are derived from the interference between the fundamental cavity mode and higher-order spatial modes of order two excited by mode mismatch. This scheme is simple, inexpensive, and, in contrast to similar techniques, first-order insensitive to beam jitter. After mitigating sources of technical noise, performance is fundamentally limited by quantum shot noise.

A scanning acoustic microscope based on picosecond ultrasonics

We report on the development of a new type of scanning acoustic microscope. We use a femtosecond light pulse to generate a short sound pulse, and then focus this sound onto the sample by means of a specially designed and microfabricated acoustic lens of radius a few microns. The sound travels to the sample through a thin layer of water. The sound reflected from the sample is collected by the lens and then passes through a monolithically integrated optical resonant cavity. The induced change in the properties of this cavity are measured using a time-delayed probe light pulse. We describe some of the challenges involved in the construction and operation of this high-precision metrology apparatus and present some preliminary results.

Optofluidic FRET microlasers based on surface-supported liquid microdroplets

We demonstrate optofluidic microlasers using highly efficient non-radiative Förster resonance energy transfer (FRET) for pumping of gain medium placed within liquid microdroplets situated on a superhydrophobic surface. Microdroplets generated from a mixture of ethylene glycol, glycerol, and water and stained with the FRET donor–acceptor dye pair Rhodamine 6G-Rhodamine 700 serve as active optical resonant cavities hosting high-quality whispering gallery modes. Upon direct optical pumping of the donor with a pulsed laser, lasing is observed in the emission band of the acceptor as a result of efficient FRET coupling between the acceptor and donor molecules. FRET lasing is characterized for different acceptor and donor concentrations, and threshold pump fluences of acceptor lasing as low as 6.3 mJ cm−2 are demonstrated. We also verify the dominance of the non-radiative FRET over cavity-assisted radiative energy transfer for the range of parameters studied in the experiments.

A Hertz-Linewidth Ultrastable Diode Laser System for Clock Transition Detection of Strontium Atoms

The frequencies of two 698 nm external cavity diode lasers (ECDLs) are locked separately to two independently located ultrahigh finesse optical resonant cavities with the Pound—Drever—Hall technique. The linewidth of each ECDL is measured to be ∼4.6 Hz by their beating and the fractional frequency stability below 5 × 10−15 between 1 s to 10 s averaging time. Another 698 nm laser diode is injection locked to one of the cavity-stabilized ECDLs with a fixed frequency offset for power amplification while maintaining its linewidth and frequency characteristics. The frequency drift is ∼1 Hz/s measured by a femtosecond optical frequency comb based on erbium fiber. The output of the injection slave laser is delivered to the magneto-optical trap of a Sr optical clock through a 10-m-long single mode polarization maintaining fiber with an active fiber noise cancelation technique to detect the clock transition of Sr atoms.

Parametrically Amplified Bright-state Polariton of Four- and Six-wave Mixing in an Optical Ring Cavity

We report experimental studies of bright-state polaritons of four-wave mixing (FWM) and six-wave mixing (SWM) signals through cascade nonlinear optical parametric amplification processes in an atom-cavity composite system for the first time. Also, the coexisting cavity transmission modes of parametrically amplified FWM and SWM signals are observed. Finally, electromagnetically induced absorption by the FWM cavity modes in the probe beam is investigated. The investigations can find potential applications in multi-channel narrow-band long-distance quantum communication.

Vacuum magnetic linear birefringence using pulsed fields: status of the BMV experiment

We present the current status of the BMV experiment. Our apparatus is based on an up-to-date resonant optical cavity coupled to a transverse magnetic field. We detail our data acquisition and analysis procedure which takes into account the symmetry properties of the raw data with respect to the orientation of the magnetic field and the sign of the cavity birefringence. The measurement result of the vacuum magnetic linear birefringence k CM presented in this paper was obtained with about 200 magnetic pulses and a maximum field of 6.5 T, giving a noise floor of about 8 × 10-21 T-2 at 3σ confidence level.

(Hg,Zn)Te Photon Detectors of Thermal Radiation

Distribution of electromagnetic wave has been determined in a typical detection structure of a photon detector. Formulas have been given for: external quantum efficiency and distribution of radiation intensity in a photosensitive element. Maximal detection parameters of (Hg,Zn)Te photoresistors have been calculated. External quantum efficiency and radiation intensity in a photosensitive element located in the optimal optical resonance cavity have been illustrated. Ultimate normalized thermal detectivity of the uncooled (T=300K) (Hg,Zn)Te photon detectors has been calculated. Slowa kluczowe: detektory fotonowe, intensywnośc promieniowania, wspolczynnik zewnetrznej wydajności kwantowej, wykrywalnośc

Optical cavity limits on higher order Lorentz violation

An optical ring cavity is used to place the first laboratory constraints on parity-odd nonrenormalizable Lorentz violation. Variations in resonant frequencies are limited to parts in $1{0}^{15}$. Absolute sensitivity to Lorentz-violating operators of mass dimension 6 is improved by a factor of a million over existing parity-even microwave-cavity bounds. Sensitivity to dimension-8 violations is improved by 14 orders of magnitude.

Synchronous control of dual-channel all-optical multistate switching

We have experimentally observed optical multistabilities (OMs) simultaneously on both the signal and generated Stokes fields in an optical ring cavity with a coherently prepared multilevel atomic medium. The two observed OMs, which are governed by different physical processes, are coupled via the multilevel atomic medium and exhibit similar threshold behaviors. By modulating the cavity input (signal) field with positive or negative pulses, dual-channel all-optical multistate switching has been realized and synchronously controlled, which can be useful for increasing communication and computation capacities.

Blue upconversion laser based on thulium-doped silica m icrocavity

Whispering gallery mode optical resonant cavities fabricated from rare-earth-doped silica glasses have demonstrated lasing from the visible through the near-IR. However, achieving lasing in the blue has been elusive. In this Letter, thulium-doped silica films are synthesized and used to fabricate toroidal optical microcavities with quality factors in excess of 10 million. Despite the high phonon energy of silica, the high circulating optical intensities present in the microcavities enable upconversion of the thulium, resulting in emission in the blue and near-IR with microwatt threshold powers that scale linearly with the concentration of the thulium.

Switching from optical bistability to multistability in a coupled semiconductor double-quantum-dot nanostructure

We investigate the optical bistability (OB) and multistability in a coupled semiconductor double-quantum-dot nanostructure inside an optical ring cavity. It is found that the transition from OB to multistability or vice versa can be easily controlled via properly adjusting the corresponding parameters of the system. Our scheme opens the possibility to optimize and control all optical switching and all optical storage devices in a coupled semiconductor double-quantum-dot nanostructure.

Faraday and Cotton-Mouton effects of helium atλ=1064nm

We present measurements of the Faraday and the Cotton-Mouton effects of helium gas at $\lambda =~1064$\,nm. Our apparatus is based on an up-to-date resonant optical cavity coupled to longitudinal and transverse magnetic fields. This cavity increases the signal to be measured by more than a factor of 270\,000 compared to the one acquired after a single path of light in the magnetic field region. We have reached a precision of a few percent both for Faraday effect and Cotton-Mouton effect. Our measurements give for the first time the experimental value of the Faraday effect at $\lambda$=\,1064\,nm. This value is compatible with the theoretical prediction. Concerning Cotton-Mouton effect, our measurement is the second reported experimental value at this wavelength, and the first to agree at better than 1$\sigma$ with theoretical predictions.