Double-pass Configuration Research Articles

Broadband, diode pumped Yb-doped fused silica laser

We report on the fabrication, optical properties and, to the first time to our knowledge, lasing characteristics of Yb-doped fused silica in bulk volume. The glass rods were manufactured by sintering of Yb-doped fused silica granulates and subsequent homogenization. Samples of various thicknesses containing doping levels of 0.27 mol% and 0.39 mol%, respectively, were investigated. The glass shows a high optical quality with refractive index variations in the 10 ppm range. We successfully demonstrated quasi-cw lasing with a maximum optical to optical efficiency of 60 % and slope efficiencies of about 70 % with respect to absorbed pump power for all samples. The laser cavity could be tuned in a wavelength range of 100 nm. The large amplification bandwidth of fused silica was verified by gain distribution measurements in a double-pass amplifier configuration.

Flat-gain wide-band erbium doped fiber amplifier by combining two difference doped fibers

A new erbium-doped fibre amplifier (EDFA) is demonstrated using a combination of newly developed Erbium Zirconia co-doped fiber (Zr-EDF) and the commercial silica-based Erbium-doped fiber (Si-EDF) as the gain medium. Both fibers have a very high concentration of erbium ion. A compact amplifier operating in C-band region is firstly reported using a double-pass configuration. It is shown that average gains of the proposed Zr-EDF amplifier are obtained at approximately 18 dB with a gain variation of ±2 dB within C-band region. A flat-gain and wide band operation is achieved by configuring the amplifier in two stages comprising a 2 m long Zr-EDF and 9 m long Si-EDF optimised for C- and L-band operations, respectively, in a double-pass parallel configuration. A chirp fibre Bragg grating (CFBG) is used in both stages to ensure double propagation of the signal and thus to increase the attainable gain in both C- and L-band regions. At an input signal power of 0 dBm, a flat gain of 15 dB is achieved with a gain variation of less than 0.5 dB within a wide wavelength range from 1530 to 1605 nm. The corresponding noise figure varies from 6.2 to 10.8 dB within this wavelength region.

Power Scaling in a Diode-End-Pumped Multisegmented Nd:YVO<inline-formula><tex-math>$_{\bf 4}$</tex-math> </inline-formula> Laser With Double-Pass Power Amplification

We demonstrate a high-power master oscillator power amplifier with the double-pass configuration based on the specially designed multisegmented Nd:YVO 4 crystals. A powerful mathematical technique on the basis of the Fourier eigenfunction expansion method is developed for precisely calculating the temperature distribution inside the gain medium. A seed Nd:YVO 4 oscillator under dual-end pumping is subsequently constructed for efficiently emitting the output power of up to 50 W. Moreover, under a total incident pump power of 244 W at 808 nm, as high as 108 W of the output power at 1064 nm is further generated in our developed master oscillator power amplifier system. Theoretical and experimental results clearly reveal that the gain medium with multiple doping concentrations is practically valuable for constructing a high-power end-pumped laser without bringing in significantly thermal effects.

Sensitization of hybrid LPFG–FBG refractometer using double-pass configuration

We demonstrated a method to enhance the sensitivity of a hybrid arc-induced Long Period Fiber Grating (LPFG)–Fiber Bragg Grating (FBG) system using a double-pass configuration for refractive index (RI) sensing. The sensing principle is based on the interrogation of the reflected signal variation of an FBG caused by the shifting of the LPFG's resonant wavelength by changes in the surrounding medium. Standard oil with RI values ranging from 1.39 to 1.49 was used to monitor the RI response of the sensor in single-pass and double-pass configurations. Comparison of both configurations showed that the double-pass configuration utilizing an optimize-coupled LPFG has a sensitivity of 870.6dB/RIU as compared to the single-pass configuration which has a sensitivity of 457.3dB/RIU in the index range of 1.43–1.46.

Gain Characteristics for C-Band Erbium Doped Fiber Amplifier Utilizing Single and Double-Pass Configurations: A Comparative Study

Gain Characteristics for C-Band Erbium Doped Fiber Amplifier Utilizing Single and Double-Pass Configurations: A Comparative Study

Compact infrared continuous-wave double-pass single-frequency doubly-resonant OPO

We demonstrate a compact continuous-wave single-frequency doubly-resonant optical parametric oscillator (DRO) in a double-pass pump configuration with a control of the relative phase between the reflected waves. The nested DRO cavity allows single longitudinal mode operation together with low threshold and high efficiency. Thermal effects are managed by chopping the pump beam, allowing continuous tuning of the emitted wavelength. The infrared idler wave (3200–3800nm) can be used for gas detection and the threshold pump power is compatible with diode pumping.

Superfluorescent bismuth-doped fibre source

We have demonstrated the first superfluorescent fibre source emitting in the range. In a double-pass configuration with an amplifier, its output power is under pumping at . Its emission spectrum has a nearly Gaussian shape, with a full width at half maximum of at the highest pump power.

Sensitive harmonic detection of ammonia trace using a compact photoacoustic resonator at double-pass configuration and a wavelength-modulated distributed feedback diode laser

A sensitive detection of ammonia in parts per billion by volume is described. The system based on photoacoustic spectroscopy (PAS) consists of distributed feedback laser diode emitting near 1,531.7 nm and a compact PA cell at double-pass configuration. In order to optimize the signal background ratio of the system, two types of modulations were tested, amplitude and wavelength modulations (WM). Using a digital lock-in amplifier, the 1f and 2f detection in WM could be investigated. A detection limit of 470 parts per million by volume could be achieved at WM-2f. In the sense of quantifing the adsorption–desorption process, the response time of the system and detection accuracy was performed in different flows. Response times between 10 and 49 s, depending on the flow rate, were obtained which enables the PA system to measure low concentrations of ammonia with high accuracy in real time.

Energy scaling of femtosecond amplifiers using actively controlled divided-pulse amplification

Divided-pulse amplification is a promising method for the energy scaling of femtosecond laser amplifiers, where pulses are temporally split prior to amplification and coherently recombined afterwards. We present a method that uses an actively stabilized setup with separated stages for splitting and combining. The additional degrees of freedom can be employed to mitigate the limitations originating from saturation of the amplifier that cannot be compensated in passive double-pass configurations using just one common stage for pulse splitting and combining. In a first proof-of-principle experiment, actively controlled divided pulses are applied in a fiber chirped-pulse amplification system resulting in combined and compressed pulses with an energy of 1.25 mJ and a peak power of 2.9 GW.

Direct amplification of a nanosecond laser diode in a high gain diode-pumped Nd:YVO_4 amplifier

We demonstrate that Nd:YVO₄ can efficiently amplify a nanosecond laser diode in a very simple double-pass configuration. Based on longitudinal pumping with a high brightness fiber-coupled laser diode at 808 nm (60 W, 100 μm, 0.22 NA) and a low Nd-doped (0.2%) temperature controlled Nd:YVO₄ we achieved an optical gain of 62 dB with very low (<2%) parasitic laser emission and an average output power of 10 W. At 15 kHz, we observed a strong gain saturation dynamic resulting in a pulse duration reduction from 100 to 3.5 ns. This effect enhances the peak power by a factor of 18 (130 kW) with an energy of 620 μJ.

COMPARATIVE STUDY ON SINGLE- AND DOUBLE-PASS CONFIGURATIONS FOR SERIAL DUAL-STAGE HIGH CONCENTRATION EDFA

A comparative study on a single- and double-pass co nfigurations for Erbium-doped fiber amplifier (EDFA ) are demonstrated using a gain media of high concentration Silica-bas ed erbium doped fiber (EDF). The amplifier has two stages comprising a 1.5 m and 9 m long EDF optimized for C-band and L-band operations respectively, in a single-pass and doubl e-pass configurations. The CFBG is used at the end of EDF stage to allow apropagation of signal and thus increases th e attainable gain in both C- and L-band spectra. At an input signal power of -30 dBm, a flat gain of 22 dB is achieved with a ga in variation of ±3 dB within a wide wavelength range from 1530 to 1600nm (C- and L-band) in double-pass configurations. The corresp onding noise figure varies from 4 to 8 dB within this wavelength region . The flat gains for single-pass configuration only amplify within 1555 nm to 1600 nm (L-band).

Fiber optical parametric amplifier with double-pass pump configuration

Characteristics of fiber optical parametric amplifier (FOPA) with double-pass pump configuration are experimentally investigated. The double-pass pump FOPA exhibits more than two-fold steeper gain slope in comparison to the conventional FOPA due to elongation of effective fiber length. In the L-band amplification band, a secondary idler is generated and used as the transmission signal in lieu of the original L-band signal. Gain measurement and bit error rate experiments are performed on the secondary idler and the results prove the usability of secondary idler, which is potentially useful for distribution networks.

Simultaneous cavity-enhanced and cavity ringdown absorption spectroscopy using optical feedback

We present a scheme of optical feedback cavity-enhanced absorption spectroscopy (OF-CEAS) including a fast optical switch to produce cavity ringdown spectra (OF-CRDS) simultaneously. This also works as a dynamically adjustable variable attenuator allowing to compensate for reduced signal levels in correspondence with absorption lines. For this, an acousto-optic deflector is used in a double-pass configuration to eliminate the single-pass frequency shift, which is incompatible with optical feedback. This is probably the most effective device providing the required fast response and the high extinction ratio necessary to perform clean ringdown measurements. The resulting direct comparison of OF-CEAS and OF-CRDS shows that these produce almost equivalent spectral data, with 0.3 % maximal difference at the top of an absorption line having a signal-to-noise ratio (S/N) of 3,300. OF-CEAS is largely winning on the short-term noise level while OF-CRDS appears to be more immune from interference fringes, delivering cleaner spectra after longer averaging.

The noise figure and gain improvement of double‐pass C‐band EDFA

ABSTRACTIn this study, the noise figure (NF) improvement is demonstrated in double‐pass C‐band erbium‐doped fiber amplifier. It is used the short length of unpumped erbium doped fiber (EDF) within a circulator‐based loop mirror which is reduced amplified spontaneous emission (ASE). The unpumped EDF attenuates part of the ASE that is then reflected back for a double pass configuration which in turn, helps to improve the gain and NF. The proposed configuration has lower NF and higher gain than conventional double pass scheme. Thus, it can be easily applied for practical application. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2525–2528, 2013

Flattening the Spectrum of Erbium-Doped Fiber ASE Source Combining with LPFG-Based Filter Technique

Through studying the basic principle of super-fluorescent fiber source and combining with internal and external gain flattening technique, the spectral flatness of erbium-doped fiber amplified spontaneous emission (ASE) source with two-stage double-pass configuration pumped by two laser diodes (LDs) is improved. By optimizing the lengths of two-stage erbium-doped fiber (EDF) and adjusting the pump power of two LDs,the powers of C-band and L-band are matching, and the spectral flatness is superior to 0.5dBm from 1535 to 1610 nm. Utilizing the long period fiber grating (LPFG)-based thermally-insensitive gain flattening filter (GFF) fabricated by ourselves, the spectral protrusion is flattened near the peak of absorption wavelength of EDF, which make the spectrum not only cover the range of C-band and L-band, also realize the spectral flatness is better than 0.8dBm in the range of 3dB bandwidth. Application of the fiber ASE source in fiber Bragg grating sensing system could decrease the multi-signal peak power imbalance.

High-stable, double-pass forward superfluorescent fiber source based on erbium-doped photonic crystal fiber

A double-pass forward configuration superfluorescent fiber source (SFS) based on erbium-doped photonic crystal fiber (EDPCF) with a high intrinsic mean wavelength stability is presented. The main factors of SFS instability with temperature variation are analyzed. Optimization of the high-stable SFS is achieved by combining high-performance EDPCF, optimal fiber length, and source structure with fine-tuning pump power. The temperature dependence of the SFS mean wavelength has been reduced to below 0.077 ppm/°C with temperature variation from 70 to −40 °C. To the best of our knowledge, this value is the closest to 0 ppm/°C in the reported references, and these new developments probably constitute an important step for high-accuracy interferometric fiber-optic gyroscope sources.

New limit on Lorentz violation using a double-pass optical ring cavity.

A search for Lorentz violation in electrodynamics was performed by measuring the resonant frequency difference between two counterpropagating directions of an optical ring cavity. Our cavity contains a dielectric element, which makes our cavity sensitive to the violation. The laser frequency is stabilized to the counterclockwise resonance of the cavity, and the transmitted light is reflected back into the cavity for resonant frequency comparison with the clockwise resonance. This double-pass configuration enables a null experiment and gives high common mode rejection of environmental disturbances. We found no evidence for odd-parity anisotropy at the level of δc/c ≲ 10(-14). Within the framework of the standard model extension, our result put more than 5 times better limits on three odd-parity parameters κ(o+)(JK) and a 12 times better limit on the scalar parameter κ(tr) compared with the previous best limits.

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.

Linear Electro Optic Effect for High Repetition Rate Carrier Envelope Phase Control of Ultra Short Laser Pulses

This paper is devoted to analyzing the principle and applications of the linear electro-optic (EO) effect for the control of the carrier-envelope-phase (CEP). We introduce and detail here an original method, which relies on the use of an EO dispersive prism pair in a compressor-like configuration. We show that, by choosing an adequate geometry, it is possible to shift the CEP without changing the group delay (isochronous carrier-envelope-phase shifter) or change the induced group delay without varying the CEP. According to our calculations, when applying an electric field around 400 V/cm to the rubidium titanyle phosphate (RTP) prisms in a double pass configuration (2 × 40 mm total length), one obtains a CEP shift of π rad at 800 nm without inducing a group delay. In contrast, this CEP shift is obtained for an electric field around 1.4 kV/cm in a RTP rectangular slab of the same total length and, in this case, the group delay is of the order of a few fs.

Spherical refractive correction with an electro-optical liquid lens in a double-pass system

In this study we show a novel double-pass configuration to correct the spherical refractive error by means of an electro-optical liquid lens. The proposed method enables spherical correction in the −12 D to +7 D range without movable parts using an electro-optical liquid lens. We have measured the optical performance of the spherical corrector in terms of power, pupil size and optical quality verifying that it fits the requirements to be applied to a double-pass system. We have also evaluated the performance of the proposed method in patients by comparison with a conventional double-pass system using a Badal optometer.