Power Laser Sources Research Articles

Tunable, high-repetition-rate, dual-signal-wavelength femtosecond optical parametric oscillator based on BiB3O6

We have demonstrated a high-repetition-rate tunable femtosecond dual-signal-wavelength optical parametric oscillator (OPO) based on BiB3O6 (BiBO) crystal, synchronously pumped by a frequency-doubled mode-locked Yb:KGW laser. The cavity is simple since no dispersion compensators are used in the cavity. The wavelength range of dual-signal is widely tunable from 710 to 1000 nm. Tuning is accomplished by rotating phase-matching angle of BiBO, and optimizing cavity length and output coupler. Using a 3.75 W pump laser, the maximum average dual-signal output power is 760 mW at 707 and 750 nm, leading to a conversion efficiency of 20.3% not taking into account the idler power. Our experimental results show a non-critical phase-matching configuration pumped by a high peak power laser source. The operation of the dual-signal benefits from the balance of phase matching and group velocity mismatching between the two signals.

Ultrafast synthesis of bifunctional Er3+/Yb3+-codoped NaBiF4 upconverting nanoparticles for nanothermometer and optical heater

We reported a simple and ultrafast route to synthesize the bifunctional Er3+/Yb3+-codoped NaBiF4 upconverting nanoparticles. It was found that the phase composition and microstructure of the prepared samples were strongly dependent on the NH4F content. When the NH4F content was 14 mmol, after 1 min reaction at room temperature, the resultant compounds exhibited pure single phase and were composed of uniform spherical nanoparticles. Under 980 nm light irradiation, the synthesized nanoparticles emitted visible emissions originating from the intra-4f transitions of Er3+ ions and the involved upconversion luminescence mechanism was associated with the typical two-photon process. With the aid of the fluorescence intensity ratio technique, the optical thermometric behaviors of the studied nanoparticle based on the (2H11/2,4S3/2) thermally-coupled levels in the temperature range of 303–483 K were systematically analyzed and the maximum sensor sensitivity was determined to be about 0.0057 K−1 at 483 K. Furthermore, the internal heating properties of the resultant nanoparticles induced by the laser power source were also studied. With elevating the pump power from 159 to 658 mW, the temperature of the upconverting nanoparticles was improved from 304 to 464 K. These results suggest that the Er3+/Yb3+-codoped NaBiF4 upconverting nanoparticles are promising bifunctional luminescent materials for nanothermometer and optical heater applications.

Raman spectra of lithium compounds

The paper is devoted to the results of investigating the spontaneous Raman scattering spectra in the lithium compounds crystals in a wide spectral range by the fibre-optic spectroscopy method. We also present the stimulated Raman scattering spectra in the lithium hydroxide and lithium deuteride crystals obtained with the use of powerful laser source. The symmetry properties of the lithium hydroxide, lithium hydroxide monohydrate and lithium deuteride crystals optical modes were analyzed by means of the irreducible representations of the point symmetry groups. We have established the selection rules in the Raman and infrared absorption spectra of LiOH, LiOH·H2O and LiD crystals.

Nonlinear pulse compression to 43 W GW-class few-cycle pulses at 2 μm wavelength.

High-average power laser sources delivering intense few-cycle pulses in wavelength regions beyond the near infrared are promising tools for driving the next generation of high-flux strong-field experiments. In this work, we report on nonlinear pulse compression to 34.4μJ-, 2.1-cycle pulses with 1.4 GW peak power at a central wavelength of 1.82μm and an average power of 43W. This performance level was enabled by the combination of a high-repetition-rate ultrafast thulium-doped fiber laser system and a gas-filled antiresonant hollow-core fiber.

3D ion velocity distribution function measurement in an electric thruster using laser induced fluorescence tomography.

Measuring the full ion velocity distribution function (IVDF) by non-intrusive techniques can improve our understanding of the ionization processes and beam dynamics at work in electric thrusters. In this paper, a Laser-Induced Fluorescence (LIF) tomographic reconstruction technique is applied to the measurement of the IVDF in the plume of a miniature Hall effect thruster. A setup is developed to move the laser axis along two rotation axes around the measurement volume. The fluorescence spectra taken from different viewing angles are combined using a tomographic reconstruction algorithm to build the complete 3D (in phase space) time-averaged distribution function. For the first time, this technique is used in the plume of a miniature Hall effect thruster to measure the full distribution function of the xenon ions. Two examples of reconstructions are provided, in front of the thruster nose-cone and in front of the anode channel. The reconstruction reveals the features of the ion beam, in particular on the thruster axis where a toroidal distribution function is observed. These findings are consistent with the thruster shape and operation. This technique, which can be used with other LIF schemes, could be helpful in revealing the details of the ion production regions and the beam dynamics. Using a more powerful laser source, the current implementation of the technique could be improved to reduce the measurement time and also to reconstruct the temporal evolution of the distribution function.

Total momentum transfer produced by the photons of a multi-pass laser beam as an evident avenue for optical and mass metrology.

The use of the radiation pressure of a laser field, as an effect of the momentum transfer of the absorbed and re-emitted photons, suggests rather a complementary than an alternative possibility for metrology to generate calibration forces or to calibrate the optical power directly traceable to the International System of Units (SI). This paper reports a method and experimentally measured evidence on options to extend the effective use of radiation pressure for generating optical forces in the sub-microNewton (μN) range. Among other features and results presented, we emphasize the variability in controlling the accuracy of these forces through the proper utilization of the power of a multi-pass laser beam (semi- or completely) locked within confined systems. The direct measurements of these forces, augmented due to the partial or total momentum transfer of the photons of a multi-pass laser beam extended from several hundreds of picoNewton (pN) up to sub-μN range for the same power of laser source, are done by a precision force measurement system and compared with basic theoretical computations. We also discuss the opportunities to probe the fundamental physical limits associated with this method and to the considerable extent other competing contributing effects that might be regarded as sources of errors in metrological tasks.

Fabrication of strong and ultra-lightweight silica-based aerogel materials with tailored properties

Cross-linked silica aerogels are promising, strong, lightweight materials for photolithographic applications. The work presented here details the preparation of ultra-lightweight aerogel materials with tailored properties through the appropriate combination of silica and methacrylate polymer using laser-induced rapid photogelation fabrication technique. For fabrication, an ethanolic solution of hexanediol diacrylate, tetraorthosilicate, Eosin Y and a tertiary amine was prepared. The amounts of reactants were varied to prepare different compositions of aerogel monoliths. The solution was irradiated with a green beam from a low power laser source. The samples, after drying in supercritical ethanol, were characterized using FTIR, BET, SEM, TGA, and a mechanical testing instrument. FTIR data suggests that neither low nor high silica content has an effect on the reactivity of acrylate functionalities during polymer formation. SEM micrographs reveal that variation in silica or polymer content does not produce any phase-separated structures. Instead, uniformly distributed nano-sized polymer–silica structures were obtained for all compositions. Our results suggest that a variety of combinations of mechanical and other properties (such as densities, surface areas, pore sizes, and pore volumes) can be produced through appropriate combination for diverse applications. All these findings provide convincing evidence that the variation of silica and/or polymer content can be used to fabricate aerogels with a variety of properties, which have the depth needed for use in laser-based 3D printing technology of simple or complex structures with nearly any dimensions.

Adaptive Tuning of Photonic Devices in a Photonic NoC Through Dynamic Workload Allocation

Photonic network-on-chip (PNoC) is a promising candidate to replace traditional electrical NoC in manycore systems that require substantial bandwidths. The photonic links in the PNoC comprise laser sources, optical ring resonators, passive waveguides, and photodetectors. Reliable link operation requires laser sources and ring resonators to have matching optical frequencies. However, inherent thermal sensitivity of photonic devices and manufacturing process variations can lead to a frequency mismatch. To avoid this mismatch, micro-heaters are used for thermal trimming and tuning, which can dissipate a significant amount of power. This paper proposes a novel FreqAlign workload allocation policy, accompanying an adaptive frequency tuning ( AFT ) policy, that is capable of reducing thermal tuning power of PNoC. FreqAlign uses thread allocation and thread migration to control temperature for matching the optical frequencies of ring resonators in each photonic link. The AFT policy reduces the remaining optical frequency difference among ring resonators and corresponding on-chip laser sources by hardware tuning methods. We use a full modeling stack of a PNoC that includes a performance simulator, a power simulator, and a thermal simulator with a temperature-dependent laser source power model to design and evaluate our proposed policies. Our experimental results demonstrate that FreqAlign reduces the resonant frequency gradient between ring resonators by 50%–60% when compared to existing workload allocation policies. Coupled with AFT , FreqAlign reduces localized thermal tuning power by 19.28 W on average, and is capable of saving up to 34.57 W when running realistic loads in a 256-core system without any performance degradation.

Design considerations and performance analysis of dual photodetector system for reliable laser wavelength and power monitoring

In this paper, a simple and low-cost sensor system based on dual photodetector for reliable laser wavelength and power monitoring, is presented. Different spectral sensitivities of Ge and InGaAs photodiodes were used to obtain ratiometric measurement of wavelength. As a signal splitter, the 2×2 fiber-optic coupler is used in order to increase further the spectral sensitivity of the system. This system is investigated with tunable laser source in the 1525–1630nm range and has showed to successfully operate in the L-range of wavelengths with high linearity of R2=0.99942. Measurement error around ±0.2nm and repeatability of ±0.16nm are achieved. By measuring system stability, the system resolution of 0.017nm is estimated. Temperature dependence of the system is investigated and measured results proved to be consistent with theory of semiconductor behavior in the function of temperature. The sensor system dependence on changing power of tunable laser source is also investigated. In the range of 4–26mW of the source optical power, the proposed sensor system shows wavelength stability of ±0.1nm.

Determination of surface heat flux and temperature using in-depth temperature data – Experimental verification

This paper presents an experimental investigation of the accuracy of two previously reported formulations of the modified one-probe calibration integral equation method (CIEM) using high temperature (to 837°C) and heat flux (to 83.1W/cm2) experimental data. The data was collected from an AISI type 304 stainless steel plug-type test sample heated with a laser power source. The one-probe CIEM requires the knowledge of the surface thermal boundary condition of a calibration test along with temperature data from one in-depth probe in order to predict the surface thermal boundary condition of an unknown (reconstruction) heating process given the temperature data from the same probe. Two modified versions of the CIEM that account for temperature dependent properties are investigated. The first modified version utilizes rescaling the time domain to account for temperature dependent thermal diffusivity and rescaling the heat flux to account for temperature dependent thermal conductivity. The Kirchhoff transformation is used in the second version to account for temperature dependent thermal conductivity while employing the same time domain rescaling approach. Seven calibration tests and six reconstruction tests were conducted which allows forty-two test cases consisting of pairs of calibration test data and reconstruction test data to be investigated. The average value of the standard deviations of the 42 net surface heat flux prediction errors obtained from the rescaling model was 0.82W/cm2. The average value of the standard deviations of the 42 surface temperature prediction errors obtained from the Kirchhoff transformation model was 1.03°C. This study demonstrates that a calibrated plug-type sensor can be used in high temperature applications to accurately reconstruct the surface heat flux and temperature of an unknown surface heating process. The stainless steel test sample is a proof of concept for a future prototype of this kind of calibrated dual measurement gauge.

Optical Parametric Amplification Techniques for the Generation of High-Energy Few-Optical-Cycles IR Pulses for Strong Field Applications

Over the last few decades, the investigation of ultrafast phenomena occurring in atoms, molecules and solid-state systems under a strong-field regime of light-matter interaction has attracted great attention. The increasing request for a suitable optical technology is significantly boosting the development of powerful ultrafast laser sources. In this framework, Optical Parametric Amplification (OPA) is currently becoming a leading solution for applications in high-power ultra-broadband light burst generation. The main advantage provided by the OPA scheme consists of the possibility of exploring spectral ranges that are inaccessible by other laser technologies, as the InfraRed (IR) window. In this paper, we will give an overview on recent progress in the development of high-power few-optical-cycle parametric amplifiers in the near-IR and in the mid-IR spectral domain. In particular, the design of the most advanced OPA implementations is provided, containing a discussion on the key technical aspects. In addition, a review on their application to the study of strong-field ultrafast physical processes is reported.

Laguerre-Gauss beam generation in IR and UV by subwavelength surface-relief gratings.

The angular momentum of light can be described by the states of spin angular momentum, associated with polarization, and orbital angular momentum, related to the helical structure of the wave front. Laguerre-Gaussian beams carry orbital angular momentum and their generation can be done by using an optical device known as q-plate. However, due to the usage of liquid crystals, these components may be restricted to operate in specific wavelengths and low power sources. Here we present the fabrication and characterization of q-plates made without liquid crystals, using processes of electron beam lithography, atomic layer deposition and dry etch techniques. We exploit the phenomenon of form birefringence to give rise to the spin-to-orbital angular momentum conversion. We demonstrate that these plates can generate beams with high quality for the UV and IR range, allowing them to interact with high power laser sources or inside laser cavities.

High power fiber lasers in the SWIR band using Raman lasers

Identifying the scope for high power laser sources around 1.6 μm band in LIDAR and free space optical communication applications, because of high atmospheric transparency in this band, we have built a high power laser that generates >25 W of output power at 1570 nm using sixth-order cascaded Raman amplification of a low power, Erbium–Ytterbium seed. A high power Ytterbium doped fiber laser operating at 1117 nm generating >100 W CW output power was built and used as the primary laser source for Raman laser experiments. We also demonstrated a novel, drive scheme for standard laser diode modules (without wavelength locking) used for pumping rare-earth doped lasers and amplifiers. This scheme improves the pumping efficiency and reliability of the laser without increasing nonlinearity in a cost effective manner.

Capabilities to improve corrosion resistance of fuel claddings by using powerful laser and plasma sources

The treatment conditions of fuel claddings of the E110 alloy by using powerful UV or IR laser radiation, which lead to the increase in the corrosion resistance at the high-temperature (T = 1100°C) oxidation simulating a loss-of-coolant accident, are determined. The possibility of the complete suppression of corrosion under these conditions by using pulsed laser deposition of a Cr layer is demonstrated. The behavior of protective coatings of Al, Al2O3, and Cr planted on steel EP823 by pulsed laser deposition, which is planned to be used in the BREST-OD-300, is studied. The methods of the almost complete suppression of corrosion in liquid lead to the temperature of 720°C are shown.

Evaluation of fluorescence emitting characteristics of a microparticle by illumination angle scanning utilizing a resin-based monolithic TAS chip

An optical sensor, such as a light waveguide implemented total analysis system (TAS), is one of the functional components that will be needed to realize a “ubiquitous human healthcare system” in the near future. We have already proposed the fundamental structure for a light waveguide capable of irradiating a living cell or particle running along a microfluidic channel, and of detecting fluorescence even from the extremely weak power of a minute particulate body. In order to foster advanced functions for obtaining information concerning the internal structure of living cells or particles conveniently, an angular scanning method that sequentially changes the direction in which the minute cell or particle is irradiated may be crucial. In this paper, we investigate fluorescence detection from resin particles attached to a fluorescent substance by switching irradiation direction of the exciting laser source power using a newly fabricated TAS chip with a unique intersection structure. To construct the experimental system cost effectively, we adopted a special light waveguide structure in which the intersection to a fluidic channel was arranged radially, with laser power inlet/outlet portions arranged in parallel. In addition, we incorporated a forced vibration mechanism on an optical fiber apex to construct a simple light-switching system. Preliminary experiments combining this unique TAS chip and the optical scanning mechanism revealed that the function of the radially arranged light waveguide switching worked adequately, and variation of transmittance of each light waveguide was accurately evaluated. Results were successfully applied to compensation of detected angular scanning signals. Finally, we performed an angular scanning experiment for a fluorescent substance attached to a microparticle under conditions of higher intersection-passing velocity of several 10s mm/s (single-shot scanning) and lower intersection-passing velocity of several mm/s (multiple-shot scanning). Based on the obtained scanning data, we successfully constructed directivities of emitting fluorescence from particles, and clarified that fluorescence emission indicated its peak at the forward and orthogonal directions of the incident light beam.

Four-fold increase in users of time-wavelength division multiplexing (TWDM) passive optical network (PON) by delayed optical amplitude modulation (AM) upstream

Abstract In this paper, we have proposed and simulated optical time division multiplexed passive optical network (TDM-PON) using delayed optical amplitude modulation (AM). Eight upstream wavelengths are demonstrated to show optical time wavelength division multiplexed (TWDM) by combining optical network units (ONU) users data at the remote node (RN). Each ONU generates 2.5 Gb/s user data, and it is modulated using novel return to zero (RZ) delayed AM. Optical TDM aggregates 10 Gb/s data per wavelength from four 2.5 Gb/s upstream user data, which facilitates four different ONU data on the same wavelength as 10 Gb/s per upstream wavelength and, simplify the laser requirements (2.5 Gb/s) at each optical network unit (ONU) transmitter. Upstream optical TWDM-PON is investigated for eight wavelengths with wavelength spacing of 100 GHz. Novel optical TDM for upstream increased the number of the simultaneous user to fourfold from conventional TWDM-PON using delayed AM with a high-quality-factor of received signal. Despite performance degradation due to different fiber reach and dispersion compensation technique, Optical TWDM link shows significant improvement regarding receiver sensitivity when compared with common TWDM link. Hence, it offers optimistic thinking to show optical TDM at this phase as one of the future direction, where complex digital signal processing (DSP) and coherent optical communication are frequently demonstrated to serve the access network. Downstream side conventional TWDM eight wavelengths are multiplexed at the OLT and sent downstream to serve distributed tunable ONU receivers through an optical distribution network (ODN). Each downstream wavelengths are modulated at the peak rate of 10 Gb/s using non-return to zero external modulation (NRZ-EM). The proposed architecture is cost efficient and supports high data rates as well as “pay as you grow” network for both service providers and the users perspectives. Users are classified into two categories viz home-user and business-user, with an option for easy up-gradation. Proposed architecture operates on next generation passive optical network stage 2 (NG-PON2) wavelength plan, with symmetrical data rate. Downstream performance is investigated by comparing, high power laser source with a conventional laser source and the L-band Erbium-doped fiber amplifier (EDFA) of gain 10 dB and 20 dB. Downstream eight wavelengths perform error-free up to 40 Km fiber reach and 1024 splitting points. Power budget of the proposed architecture incorporates the N1, N2, E1 and E2 optical path loss class.

Intrinsically stable high-power single longitudinal mode laser using spatial hole burning free gain

A fundamental advantage of lasers is their ability to produce a large number of photons in a single optical mode, yet this is achieved in only a minor fraction of devices due to the instability mechanism called spatial hole burning. Here, we exploit the spatial hole burning free nature of a stimulated scattering gain medium to demonstrate single longitudinal mode (SLM) operation in a generic standing wave cavity. A continuous wave diamond Raman oscillator with multi-Watt-level output power and a frequency stability of 80 MHz is demonstrated without use of additional mode-selective elements. Mode stability is addressed by considering the coupling of the Stokes power with thermally induced optical path length changes in the gain medium. The results foreshadow a novel approach for greatly extending the power and wavelength range of SLM laser sources, and with potential advantages for achieving sub-Poissonian intensity noise and sub-Schawlow–Townes linewidths.

Inverse Prediction of Temperature Through Time Rescaling of High-Temperature Experimental Data

This paper presents experimental data from a two-layer test sample made up of a copper layer and an AISI type 316 stainless steel (SS) layer that was heated with a laser power source. Experiments were conducted to generate high-temperature benchmark data that ranged from room temperature to 820 °C. The concept of time rescaling was employed to account for the dependence of thermal diffusivity on temperature in order to utilize the calibration integral equation method (CIEM). The future time regularization method was used to obtain a stable prediction for the surface temperature. An estimate for the future time regularization parameter was acquired through analysis of the in-depth calibration test thermocouple (TC) response. Results for three test cases consisting of selected pairs of calibration data and reconstruction data (to be predicted) are presented and discussed. Four different values of the future time regularization parameter were employed in the three test cases. The proposed nonlinear (NL) formulation improved the prediction accuracy when compared to the constant properties formulation of the CIEM. It should be emphasized that no knowledge of TC probe depth or TC response properties is required.

Beam Combining of SOA-Based Bidirectional Tunable Fiber Nested Ring Lasers With Continuous Tunability Over the C-band at Room Temperature

Nested ring cavities are used to develop a simple compact, low-cost semiconductor optical amplifier (SOA)-based bidirectional tunable fiber ring laser source. We propose a bidirectional tunable fiber ring laser structure based on ( N > 1) number of SOAs that has a great potential for achieving a high power laser source that uses low-power optical components by coherently coupling the nested ring cavities. A commercial tunable filter is used to deliver a wavelength tuning range of 30 nm. The lasing tunable range can be further changed by using SOAs with operating wavelengths in different regions of the optical spectrum. The output power of the bidirectional fiber ring resonator with three SOAs was around 3.5 times larger than the output of a single SOA fiber ring laser (i.e., 17.7 versus 5.14 mW) at 1550 nm wavelength. The optical signal-to-noise ratio was measured to be up to +49 dB, wavelength stability was ±0.015 nm, and optical power stability was better than ±0.2 dB.

A laboratory model of post-Newtonian gravity with high power lasers and 4th generation light sources

Using the post-Newtonian formalism of gravity, we attempt to calculate the x-ray Thomson scattering cross section of electrons that are accelerated in the field of a high intensity optical laser. We show that our results are consistent with previous calculations, suggesting that the combination of high power laser and 4th generation light sources may become a powerful platform to test models exploring high order corrections to the Newtonian gravity.