Single Etalon Research Articles

Watt-level widely tunable narrow-linewidth pulsed mid-infrared MgO:PPLN optical parametric oscillator with a F-P etalon

A watt-level, widely tunable, narrow-linewidth pulsed MgO:PPLN optical parametric oscillator using a single etalon is demonstrated above 3 µm for the first time, to the best of our knowledge. The pump source is an acousto-optical Q-switched Nd:YAG laser at 1064 nm with a pulse duration of 220 ns and a repetition rate of 10 kHz. Employing a V-shaped cavity configuration, the emission wavelengths of the OPO can be tuned in the range of 3.64 µm − 3.8 µm and 1478 nm − 1503 nm by varying the temperatures of the MgO:PPLN crystal between 37℃ and 146℃. Under a pump power of 22.5 W, a maximum average output power of 2.12 W at 3.74 µm is achieved with a theoretical linewidth of 0.3 nm at the temperature of 79.6℃, corresponding to a pulse width of 145 ns and a peak power of 1.46 KW. At the same time, a maximum signal power of 2.86 W at 1486.66 nm is obtained with a linewidth of 0.03 nm, corresponding to a pulse width of 190 ns and a peak power of 1.51 KW.

SLM operation of a high repetition rate BBO Optical Parametric Oscillator pumped by DPSSL at 355 nm

Single longitudinal mode (SLM) operation of a high repetition rate (1 kHz) nanosecond Type-II BBO optical parametric oscillator (OPO), pumped by the third harmonic (355 nm) of a Diode Pumped Solid State Laser (DPSSL), is demonstrated using a single intra-cavity etalon. Implementation of the cylindrical focusing configuration of the pump beam along with its double passing geometry through the nonlinear OPO crystal has facilitated a low threshold (~0.7 mJ/pulse @355 nm) operation with narrow spectral linewidth (~150 GHz) output. Operations of the OPO at such a low threshold has enabled to maneuver insertion of an intra-cavity etalon for further reducing the spectral linewidth, which allows the OPO to provide SLM lasing output over the spectral range 500–600 nm. The spectral characteristics of the SLM OPO are studied in detail. The time-averaged spectral linewidth of the SLM OPO is measured to be less than 250 MHz.

Fiber-based angular filtering for high-resolution Brillouin spectroscopy in the 20-300 GHz frequency range.

Brillouin spectroscopy emerges as a promising non-invasive tool for nanoscale imaging and sensing. One-dimensional semiconductor superlattice structures are eminently used for selectively enhancing the generation or detection of phonons at few GHz. While commercially available Brillouin spectrometers provide high-resolution spectra, they consist of complex experimental techniques and are not suitable for semiconductor cavities operating at a wide range of optical wavelengths. We develop a pragmatic experimental approach for conventional Brillouin spectroscopy that can integrate a widely tunable excitation-source. Our setup combines a fibered-based angular filtering and a spectral filtering based on a rotating single etalon and a double grating spectrometer for sequential reconstruction of Brillouin spectra. This configuration allows probing confined acoustic phonon modes in the 20-300 GHz frequency range with excellent laser rejection and high spectral resolution. Remarkably, our scheme based on the excitation and collection of the enhanced Brillouin scattering signals through the optical cavity allows for better angular filtering with decreasing phonon frequency. It can be implemented for the study of cavity optomechanics and stimulated Brillouin scattering over broadband optical and acoustic frequency ranges.

A single-frequency intracavity Raman laser

A continuous-wave (CW) single-longitudinal-mode (SLM) intracavity Raman laser is demonstrated for the first time, by virtue of the spatial hole-burning free nature of stimulated Raman scattering (SRS) gain. By using a single etalon in the Nd:GdVO4 fundamental laser cavity, the spectral linewidth of the multimode fundamental field is suppressed below the Raman linewidth of Raman crystal BaWO4; hence power in all the longitudinal modes of fundamental field can be extracted by one single Stokes mode. Therefore, the hole-burning free SRS gain exhibits a spectral cleanup effect whereby a stable SLM Stokes field is derived from the multimode fundamental field within a simple standing-wave cavity arrangement. The low-threshold SLM Raman laser delivered 3.42 W SLM Stokes and 1.53 W SLM one-way yellow harmonic at the guide-star wavelength of 589.16nm. The results here provide a new approach to SLM laser operation with good simplicity and power dynamic range. Further engineering for power scaling and better stability is also discussed.

Single etalon design for two-stage cross-axis VIPA spectroscopy.

Two-stage cross axis VIPA spectrometers have been widely used in Brillouin microscopy since they provide single shot spectral measurements at high throughput and extinction. However, this spectrometer configuration presents challenges such as size, cost and alignment difficulties between the two cascaded etalons. Here, we present a cross-axis VIPA spectrometer that implements a single etalon, using a light recirculation architecture to achieve the multistage configuration.

1.4 µm continuous-wave diamond Raman laser.

The longest wavelength (~1.4 µm) emitted by a diamond Raman laser pumped by a semiconductor disk laser (SDL) is reported. The output power of the intracavity-pumped Raman laser reached a maximum of 2.3 W with an optical conversion efficiency of 3.4% with respect to the absorbed diode pump power. Narrow Stokes emission (FWHM <0.1 nm) was attained using etalons to limit the fundamental spectrum to a single etalon peak. Tuning of the Raman laser over >40 nm was achieved via rotation of an intracavity birefringent filter that tuned the SDL oscillation wavelength.

The Brazilian Tunable Filter Imager for the SOAR Telescope

ABSTRACTThis article presents a description of a new Tunable Filter Instrument for the SOAR telescope. The Brazilian Tunable Filter Imager (BTFI) is a highly versatile new technology to be used both in seeing-limited mode and at higher spatial fidelity using the SAM Ground-Layer Adaptive Optics facility (SOAR Adaptive Module) which is being deployed at the SOAR telescope. Such an instrument presents important new science capabilities for the SOAR astronomical community, from studies of the centers of nearby galaxies and the insterstellar medium to statistical cosmological investigations. The BTFI concept takes advantage of three new technologies. The imaging Bragg Tunable Filter (iBTF) concept utilizes Volume Phase Holographic Gratings in a double-pass configuration as a tunable filter, while a new Fabry-Perot (FP) concept involves the use of commercially available technologies which allow a single FP etalon to act over a very large range of interference orders and hence spectral resolutions. Both of these filter technologies will be used in the same instrument. The combination allows for highly versatile capabilities. Spectral resolutions spanning the range between 25 and 30,000 can be achieved in the same instrument through the use of iBTF at low resolution and scanning FPs beyond R ∼ 2,000 with some overlap in the mid-range. The third component of the new technologies deployed in BTFI is the use of EMCCDs, which allow for rapid and cyclical wavelength scanning thus mitigating the damaging effect of atmospheric variability through the acquisition of the data cube. An additional important feature of the instrument is that it has two optical channels which allow for the simultaneous recording of the narrow-band, filtered image with the remaining (complementary) broadband light. This avoids the otherwise inevitable uncertainties inherent in tunable filter imaging using a single detector, which is subject to temporal variability of the atmospheric conditions. The system was designed to supply tunable filter imaging with a field-of-view of 3′ on a side, sampled at 0.12″ for direct Nasmyth seeing-limited area spectroscopy and for SAM’s visitor instrument port for GLAO-fed area spectroscopy. The instrument has seen first light, mounted on the SOAR telescope, as a visitor instrument. It is now in commissioning phase.

Wide-band single-shot measurement of refractive indices and birefringence of transparent materials

A new approach to measure the refractive index of a given material, in its whole transparency window and within a single-shot, is proposed. This method, which requires the use of only few and common optical elements, is based on the analysis of the transmission function of a single etalon fabricated with the material under test, and can be used also to directly evaluate the sample birefringence with high accuracy. Method's effectiveness is verified on both isotropic and birefringent samples with known optical properties in the 0.7–1.65μm wavelength range. Using the proposed method, the refractive index can be estimated with accuracy of the order of 10−4.

Performance enhancement scheme for RSOA-based WDM-PONS by using a single Fabry-Perot etalon

A scheme for simultaneous extinction ratio enhancement, optical frequency stabilization, and wavelength reuse is proposed for reflective semiconductor optical amplifier-based wavelength-division-multiplexed passive optical networks to stabilize the optical channel frequency and enhance bidirectional transmission.This is achieved by simply employing a single Fabry-Perot etalon at the optical line terminal rather than having one at each optical network unit. Compared with the remodulation scheme that uses a 10-Gb/s optical signal with a 3-dB extinction ratio as a downstream optical signal and a seed light, our scheme shows improvements in power penalties greater than 1.8 dB and 1.4 dB for 10-Gb/s downstream and 1.25-Gb/s upstream signals, respectively, after transmission of 25 km at a bit-error-rate = 10−9. Moreover, a power penalty of only 0.5-dB is observed in comparison to the two 1.25-Gb/s upstream bit-error-rate results based on using a continuous-wave seed light and a data-erased seed light. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26178

A newly designed single etalon double edge Doppler wind lidar receiving optical system

A new optical Doppler lidar receiving system which can measure Doppler-shifted incoherent scattering light has been proposed and tested. This system functions in a manner similar to two edge filters and consists of a single etalon, a polarization beam splitter, and mirrors that can guide scattered light into a single etalon with two different angles. These two incident angles are precisely adjusted by the polarization beam splitter and mirrors. Using this optical receiving system we can measure a moving target with a high sensitivity. Theoretical calculations show that this system will have a better optical sensitivity than a single edge system and will allow the use of incoherent Doppler lidar for wind velocity measurements.

TIMED Doppler Interferometer on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics satellite: Data product overview

The TIMED Doppler Interferometer (TIDI) performs the measurement of upper atmospheric winds on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite. This is an optimized single etalon Fabry Perot interferometer that records the slight Doppler shift of individual emission features of the O2 (0,0) atmospheric band. The interferometer operates at a 100% duty cycle obtaining neutral wind altitude profiles on a global basis. The measurements are synoptic and provide an uninterrupted long‐term climatological record of the dynamics in the mesosphere and lower thermosphere regions. The data products from TIDI include (1) apparent line of sight winds and integrated brightness, (2) inverted line of sight winds and volume emission rate, and (3) inverted horizontal neutral wind fields on an evenly spaced track angle/altitude grid. The data products demonstrate an interannual variability in the tidal structure of the mesosphere and the lower thermosphere and an inherent daily geophysical variance.

A single-fringe etalon silicon pressure transducer

This paper describes the development of an interferometric pressure transducer using a single etalon fringe as an intensity mode signal for a deflectable silicon diagram. The last fringe before the mechanical contact of the two etalon surfaces is employed, thus, providing an integral overpressure limit. The etalon design permits the illumination source to be only approximately monochromatic thereby allowing a conventional LED to be used in place of the laser diode normally required in interferometric designs and greatly simplifies the pressure sensor and instrumentation package.

ZnGeP_2 optical parametric oscillator with 38–124-µm tunability

A ZnGeP>(2) (ZGP) optical parametric oscillator (OPO) with wide mid-IR tunability has been demonstrated. The singly resonant angle-tuned ZGP OPO was pumped by 100-ns erbium laser pulses at lambda =2.93mum and yielded output that was continuously tunable from 3.8 to 12.4 mum (type I phase matching) and from 4 to 10 mum (type II phase matching). An OPO pump threshold was less than 1 mJ in the whole 4-12 mum range of the output, and the quantum conversion efficiency reached 35%. An OPO linewidth was typically a few wave numbers; however, with a single intracavity etalon (uncoated Si plate) in a type II OPO it was narrowed to <0.5cm(-1). We demonstrate the sensitive detection of N(2)O gas with the narrow-linewidth OPO.

Efficient, single frequency, high repetition rate, PPLN OPO pumped by a prelase Q -switched diode-pumped Nd:YAG laser

Single axial mode operation (<200 MHz optical bandwidth) of a high repetition rate periodically poled lithium niobate optical parametric oscillator (OPO) has been obtained at signal wavelengths between 1.46 μm and 1.64 μm. OPO signal slope efficiencies of 35% have been measured for repetition rates of 5–20 kHz. Single mode operation required spectral narrowing of both the pump laser and the OPO. A simple technique of prelase Q-switching was implemented to reduce the optical bandwidth of the cw diode-pumped Nd:YAG pump laser to <1 GHz. A single intracavity etalon was then sufficient to ensure single frequency oscillation of the OPO signal. The OPO output was stable with a smooth spatial profile and an M2 value of 1.3.

Efficient single-frequency pulsed periodically poled lithium niobate optical parametric oscillator

Single axial mode oscillation (<500 MHz bandwidth) of a pulsed Nd:YAG pumped periodically poled lithium niobate optical parametric oscillator has been obtained. A single intracavity etalon was sufficient to produce single frequency operation for operating signal wavelengths between 1.45 and 1.6 μm. The oscillation threshold increase from the free-running case was between 1.5 and 2.1 times, and pump depletions of 40–60% were measured across the tuning range. Parasitic processes based on optical parametric generation and cascaded oscillation have been minimised.

The Doppler Rayleigh lidar system at Arecibo

The instrument structure and the operation of a Doppler Rayleigh lidar located at the Arecibo Observatory in Puerto Rico are described. The device consists of an injection seeded, frequency doubled, Nd:YAG laser coupled with a small Newtonian telescope and a single etalon, Fabry-Perot interferometer in its receiver. With this combination of transmitter and receiver, observations of the Doppler spectral components of the Rayleigh backscattered signal from the atmosphere are possible. Neutral wind and temperature up to mesospheric heights are presented. The improvements to the instrument that are underway, which will allow an increase in the temporal and spectral sampling of the winds, are discussed. >

Initial Doppler Rayleigh lidar results from Arecibo

We present the first results of the operation of a Rayleigh lidar from the Arecibo Observatory. The device consists of an injection seeded, frequency doubled, Nd:YAG laser coupled with a single etalon, Fabry‐Perot interferometer in the receiver, the combination of which permits Doppler observations of the backscattered spectral emission from the mesosphere. The measured winds from our initial experiments show a great deal of variability on time scales that appear to be less than the hour that it takes to measure a wind profile with the present system.

A high power dye laser pumped by a crowbar mode flashlamp

A flashlamp pumped dye laser system is described. The flashlamp works in the crowbar mode and was especially developed for this laser system. The laser has been operated with rhodamine 6G (λ ≈ 600 nm) and coumarine 1H (λ ≈ 470 nm) with an output energy of up to 1 J per pulse. With a single etalon a linewidth of 0.2 nm was achieved in a pulse of 3–6 μs length. The maximum repetition rate is 2 pps, limited by the high voltage power supply.

Angle-tuned etalon filters for optical channel selection in high density wavelength division multiplexed systems

Applications are discussed for angle-tuned in-line Fabry-Perot etalons for optical channel selection in a high-density wavelength division multiplexed (WDM) direct-detection fiber system. A typical WDM application (LAMBDANET type) was described. Different demultiplexing techniques and their relative advantages were considered. Design guidelines are given for determining the etalon parameters, the minimum channel spacing and the maximum number of channels for a single etalon and multiple etalons, including stacked identical etalons and stacked nonidentical etalons. Experimental results on using these etalons for optical channel tuning in a multiwavelength WDM optical communication system are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The gain-bandwidth of an InSb transphasor

Detailed results are presented of two-beam optical transistor (transphasor) studies in a single InSb etalon using a CW CO laser to provide the bias beam and a Pb S 1-x SE x diode laser to generate a modulated signal. The gain-bandwidth product has been measured to be ∼ 1.2 MHz for gain values ≥ 3 and is reduced at lower gain. A full expression for the absolute value of the optical gain is derived and shows good agreement with these results. An experimental method to estimate the device and material response time through the gain/ frequency dependence is presented. A medium response time of 230 ns ± 10 percent has been deduced for the conditions of these experiments.