Output Characteristics Of Laser Research Articles

Crystal host engineering for transition metal lasers

Much progress has been made in the power and energy scaling of mid-infrared lasers based on transition metal ions, such as Cr2 + , Co2 + , and Fe2 + , in zinc and cadmium chalcogenides. Still, the exploration of the physics of these devices is incomplete. In this work, we analyze absorption spectra collected from Fe2 + ions in several binary, ternary, and quaternary host crystals at temperatures from a few degrees Kelvin to room temperature. We use the zero-phonon lines of the low-temperature spectra to calculate the value of the crystal field energy of Fe2 + ions in these hosts. We plot these crystal field energies with respect to the anion–cation distance of the host crystal and show that their crystal field strengths deviate somewhat from the trend predicted by crystal field theory. We use a model which we previously developed to describe the upper state lifetime of Fe2 + ions to predict the steady-state radiative efficiency of Fe:II–VI materials with respect to temperature. The impact of relative crystalline disorder on the output characteristics of lasers based on Cr:ZnS, Cr:ZnSe, Fe:ZnSe, and Fe:CdMnTe is explored. The effect of decreased long-range order of the host crystal is observed in the broadening of the absorption spectra of Fe2 + -doped ternary and quaternary alloys, the broadening of the spectral linewidth of continuous-wave Fe:II–VI lasers, and a reduction in the portion of the Cr:ZnSe emission spectrum accessible for modelocked lasing. This survey provides a richer picture of the tradespaces that can be leveraged when producing laser devices based on transition metal chalcogenides.

Optofluidic lasers and their applications in biochemical sensing.

Optofluidic laser (OFL) technology, as an emerging technology combining microfluidics and laser technology, offers many unique advantages in sensing applications and has become a research hotspot for highly-sensitive intracavity biochemical analysis. Biochemical sensors based on OFLs can detect changes in biochemical parameters by using significant changes in laser output characteristics, so as to achieve high detection sensitivity. Here, we provide an overview of OFLs with a focus on their constructions, the design of OFL-based biochemical sensors, and their applications in biochemical analysis. Firstly, the three elements of an OFL, including the optical microcavity, gain medium, and pump source, are described systematically. After explaining the basic principles and characterization of OFLs for biochemical sensing, the current research progress of OFL-based biochemical sensors is summarized and analyzed according to the combination of OFLs with different assay techniques. This is followed by a discussion of the research on OFLs at the level of biological macromolecules, cells, and tissues. Finally, in view of the applications of OFLs in the field of biochemical sensing, the current challenges and future development directions are briefly discussed.

Analysis of preionization effect of excimer laser

Excimer laser plays an important role in the national economic production because of its short wavelength, high repetition frequency and large energy. In the output characteristics of excimer lasers, high beam quality and high energy stability are the characters of high-end excimer light source, and whether the excimer laser system can sufficiently develop the preionization process is the key to output laser pulses with high beam quality and stable energy. This paper is mainly to study the preionization process of ArF excimer laser, and establish one-dimensional simulation calculation model and two-dimensional simulation calculation model. Based on the fluid calculation method of Comsol Multiphysics software, the numerical simulation analysis and calculation are carried out, with the study focusing on the ionization wave propagation process in the preionization process and the relationship between preionization and main discharge. The results show that the spatial structure of corona rod and main electrode should be considered comprehensively when an excimer laser system is designed. Appropriate preionization structure and voltage can make the main discharge triggered during the maintenance of free electrons, which can effectively reduce the discharge voltage, avoid streamer and arc discharge, and improve the output beam quality and system energy stability.

Output characteristics of an all-fiber laser with a 2-μm MOPA structure

The predecessor of China Optics was China Optics and Applied Optics Digest, which was founded in 1985. At that time, it was the only retrieval journal in the field of optics in China. At the end of 2008, China Optics and Applied Optics Digest was renamed

In-Well and Barrier Coupling Pump of Semiconductor Disk Laser

We report an in-well and barrier coupling pump scheme of semiconductor disk laser (SDL). An in-well-absorbed (940 nm) and a barrier-absorbed (808 nm) pump source were used to measure laser output characteristics. The output power of the coupling pump can be significantly improved compared to the in-well pump only scheme under similar thermal load conditions. The power scaling of the coupling pump SDL is caused by the interaction dynamics of the photoexcited carrier between quantum-well and barrier. The results are discussed with a rate equation model that considers the injected into the quantum-well carrier and the barrier carrier in the active region.

Influence of Linewidth Enhancement Factor on the Nonlinear Dynamics and TDS Concealment of Semiconductor Ring Lasers

In this paper, the influences of linewidth enhancement factor on the output characteristics of a semiconductor ring laser (SRL) are numerically investigated. By constructing a master–slave injection model, we discuss the influence of linewidth enhancement factor on the output characteristics of SRL. In addition, the 0–1 chaos test is introduced to study the effects of linewidth enhancement factor, feedback strength, feedback time delay and normalized injection current on the dynamic characteristics of the master laser. Furthermore, a simulation study is carried out on the suppression of time delay characteristics by the linewidth enhancement factor. The results show that selecting a proper linewidth enhancement factor has a significant effect on the chaotic output of SRL, and a larger linewidth enhancement factor is beneficial for the concealment of time delay signature. Such results are beneficial for achieving the security chaos communication and physical random generators.

Switchable multi-wavelength thulium-doped fiber laser using a two-taper fiber filter

An individually switchable and tunable multiwavelength thulium-doped fiber laser (TDFL) is proposed and experimentally demonstrated. The key component of the laser is a comb filter composed of two fiber tapers separated by a short middle section. A nonlinear loop mirror (NOLM) is inserted into the laser cavity to suppress the intense gain competition. By properly adjusting the polarization controllers (PCs) in the cavity, the laser can operate in at most sextuple wavelength state. In addition to these laser output characteristics, the experiment result also shows that single wavelength tuning can be achieved, and the tuning range is 1952.06 nm to 1975.62 nm. This multi-wavelength TDFL may be useful in optical fiber sensing or other fields desiring flexible optical source.

Investigation on the self-starting Mamyshev oscillator with low threshold

We have demonstrated a mode-locked Mamyshev oscillator based on a single-mode-fibre configuration with low threshold. The influences of spectral filters and the pump power on the output laser characteristics have been investigated. In the case with spectral-filter central wavelength far away from the peak of gain spectrum, the laser pulses have deviated slightly from similariton evolution with gain-shaping under high pump power. Moreover, self-starting mode-locking operation has been realized when the pump power was only 520 mW, which might benefit from the appropriate polarization conditions and small spectral filter separation. The laser can generate 1.89 nJ ultra-short pulses with 20 dB spectral width of 54.6 nm. The pulse duration can be compressed externally to 64.69 fs with the peak power of 21.3 kW.

Dual-loss-modulated Q-switched YVO4/Nd:YVO4 laser based on both Bi2Se3 and Cr4+:YAG

A dual-loss-modulated Q-switched laser at 1.06 µm is investigated. Bi2Se3 and Cr4+:YAG saturable absorber were simultaneously inserted into a laser cavity and used to study output characteristics of Q-switched laser at 1.06 µm. The obtained shortest pulse width, repetition rate and maximum single pulse energy were 240 ns, 140 kHz, and 2.57 μJ, respectively. Compared with those obtained in Q-switched laser with single Bi2Se3 SA, the pulse width is compressed by 70% and peak power increases 3.3 times. The results show that Bi2Se3 is a promising material for all-solid-state Q-switched laser and dual-loss-modulated technique is an effective method to optimize the output characteristics of Q-switched laser with two-dimensional materials.

Blue-pumped single-longitudinal-mode deep red band Pr: YLF Laser

This paper reports the single-longitudinal-mode (SLM) laser output of Pr: YLF at 721.2 nm by inserting double Fabry–Perot(F–P) etalons into the cavity. We use the correlation rate equation model to simulate the laser output characteristics and combine the results to design and conduct experimental research. By selecting the F–P etalon with appropriate thickness, when the maximum absorbed pump power is 2605 mW, this SLM solid-state laser achieved a maximum output power of 509 mW. The slope efficiency is 20.8%, and the optical–optical conversion efficiency is 19.5%. The emission spectrum has a linewidth of about 50 MHz. This study is the first time that Pr: YLF crystal has achieved single-frequency laser output in the band of deep red light by the double F–P etalons mode selection method. It lays a foundation for the broad application of SLM deep red laser.

CuCrO2 nanoparticles-polyimide films as saturable absorber for improving the output characteristics of passively Q-switched in ytterbium doped fiber lasers

CuCrO2 (CCO) Nanoparticles (NPs)-Polyimide (PI) films are successfully used to achieve passively Q-switched pulse output in ytterbium-doped fiber lasers (YDFL). The laser output characteristics can be regulated by using our as-fabricated CCO NPs-PI films at 1.03 μm. The pulse duration and repetition rate are simultaneously compressed by tens of times, at the same time single pulse energy and peak power are increased by one and three orders of magnitude, respectively. In particular, this is the first time that pulse duration and repetition rate are compressing simultaneously in YDFL. In addition, CCO NPs is integrated into YDFL for the first time. The reason for these phenomenons is that reverse saturable absorption reasonably increases the cavity loss, which effectively improves the modulation depth, over threshold degree and the accumulation of inversion particles. All these can prove that CCO NPs can be used as an important SA to construct high-performance Q-switched fiber laser.

Fabrication of Sb2O3 by an improved chemical reaction assisted vertical micro sublimation method and its saturable absorber performance

Two-dimensional molecular crystals (2DMCs) are emerging ideal materials for future high-performance optoelectronic devices. People are constantly exploring new methods to solve the problem of difficult growth. Here, we design an improved chemical reaction-assisted vertical micro sublimation method based on vertical micro sublimation for the growth of two-dimensional Sb2O3 inorganic molecular crystals for the first time. The saturation absorption characteristics of the self-made Sb2O3 2DMCs were systematically tested, and the Q-switched laser output characteristics of Sb2O3 2DMCs at 1 µm were verified by using Nd: GYAP mixed crystal. The maximum average output power of 231 mW was achieved at 1080.6 nm, corresponding shortest pulse with a duration of 472 ns and maximum pulse repetition rate of 376 kHz. The maximum single pulse energy and the maximum peak power of the laser output were 0.614 µJ and 1.3 W, respectively. The growth of other 2DMCs would be motivated and its potential applications in the field of ultrafast photonics would be expanded with our findings.

Tunable and switchable multi-wavelength actively Q-switched fiber laser based on electro-optic modulator and an improved Sagnac filter

A switchable and tunable multi-wavelength actively Q-switched erbium-doped ring fiber laser based on electro-optic modulator (EOM) and an improved Sagnac filter is proposed and demonstrated. The number of maximum wavelengths obtained is seven in the laser. The maximum wavelength tuning ranges of single and dual-wavelength outputs are about 11 nm and 7 nm respectively. The triple, quadruple and quintuple-wavelength outputs with different kinds of wavelength intervals are obtained. By continuing to adjust the polarization controllers (PCs), the six and seven-wavelength outputs with same intervals are also obtained in this laser. Under the condition of maximum pump power, the maximum output power is 58 μW and the minimum pulse width is less than 2 μs. For the laser output characteristics, the maximum wavelength drift and power fluctuation are 0.17 nm and 0.56 dB respectively.

Saturable absorption and its consequent effects in bistable erbium-doped fiber ring laser

The linear absorption in erbium-doped fiber (EDF) contributes to its excellent role in EDF amplifiers and lasers. A nonlinear optical contribution in the absorption of EDF is responsible for optical bistable action when it is present in a laser cavity. To quantify this effect, the variation of absorption coefficient is measured at different signal powers at multiple wavelengths in the C-band for different EDF lengths, and saturable absorption parameters such as the saturation power are extracted. Then the modification in the output characteristics of EDF ring laser with change in fiber length and in the presence of self-induced saturable absorption effect within the gain medium, which leads to optical bistability, is measured. By comparing the measured parameters obtained from saturable absorption in EDF and optical bistability in EDF ring laser, we estimated the length of the gain medium which acts as the saturable absorber inside the cavity of the laser. This is useful in constructing bistable lasers with optimized conditions. The temporal evolution of cavity loss and gain with the intra-cavity power and up- and down-thresholds helps in understanding why the down-threshold will be lesser than the up-threshold in bistable laser systems.

Effect of buffer gas on gas temperature distribution and output characteristics of flowing-gas circulation cesium vapor laser

Effect of buffer gas on gas temperature distribution and output characteristics of flowing-gas circulation cesium vapor laser

The influence of axial offset of fusion splicing on a large mode area fiber based oscillator

Fiber oscillators have the potential for achieving high power, high beam quality lasers with simple and compact structure, of which the fusion splicing point is an important aspect to the laser output characteristics. A model taking into account the axial offset of the splicing point and spatial mode competition has been proposed to analyze the mode interaction of a large mode area fiber based oscillator. The calculated results show that the axial offset of the output side fusion point has the main influence on the laser output beam quality, but the axial offset would not obviously reduce the optical efficiency, especially when the value is smaller than 2 μm. The influence of cavity parameters on the laser output characteristics under the existence of splicing point with axial offset has also been discussed. This model can provide a method for analyzing the mode dynamic that may be helpful for understanding the mode interactions in fiber oscillators.

Experimental and Theoretical Study of an Actively Q-Switched Tm:YLF Laser with an Acousto-Optic Modulator.

We report the characteristics of a diode-end-pumped, high-repetition-rate, acoustic-optic (AO) Q-switched Tm:YLF laser operating from 5 kHz to 10 kHz. In the continuous-wave (CW) regime, a maximum average output power of 8.5 W was obtained with a slope efficiency of 30.7%. Under the AO Q-switching regime, a maximum output power of 7.32 W was obtained at a repetition frequency of 5 kHz with a pulse width of 68 ns and a pulse energy of 1.4 mJ, corresponding to a peak power of 21.5 kW. A time-dependent rate equation model is introduced to theoretically analyze the results obtained in the experiment, in which the cross-relaxation phenomenon, upconversion losses and ground-state depletion are taken into account. Additionally, the evolution processes of population inversion density and intracavity photon number density with time are also presented. The theoretical results well predict the dependence of laser output characteristics of Tm:YLF crystal on the incident pump powers.

Transversely pumped solar Nd3+-doped fiber laser

In order to improve the coupling efficiency of solar fiber lasers, a new kind of transversely pumping geometry is proposed. A two-stage concentration system is designed to concentrate the sunlight into the Nd-doped fiber coiled in a ring chamber with high-reflective inner surfaces. The primary concentrator is an off-axis Fresnel lens with a radius of 600 mm, and the secondary concentrator is a compound parabolic optical waveguide. With this concentration configuration, the collection efficiency can be as high as 21.4%. 73.5 W solar power is absorbed by the fiber core according to ray-tracing simulation. Output characteristics of the solar fiber laser are further analyzed by calculating the rate equations. 2.6 W laser output is obtained and the slope efficiency reaches 3.7%.

Output characteristics regulation of Q-switched fiber laser by Fe3O4 nanoparticle-polyimide film

Fe 3 O 4 (FO) nanoparticles (NPs) - polyimide (PI) film was used as saturable absorber (SA), and achieved passive Q-switched output at 1.5 μm successfully. Based on the reverse saturable and saturable absorptions of FO NPs-PI film, the laser output characteristics can be further optimized by adjusting the ratio of FO NPs to PI. When the ratio of FO NPs to PI is 1:5 (FO NPs-PI (1:5)), the pulse duration and repetition rate are 0.669 μs and 5.51 kHz; this is the first time to realize the simultaneous compression of repetition rate and pulse duration. The single pulse energy and peak power are up to 364 nJ and 556 mW. The optical conversion efficiency can reach 855%, and it is about two orders of magnitude higher than other reports. The results show that it is helpful to construct high performance Q-switched pulse laser by introducing proper cavity loss through reverse saturable absorption. • Fe 3 O 4 (FO) nanoparticles (NPs) - polyimide (PI) film was used as saturable absorber (SA). • By introducing proper cavity loss through PI's reverse saturable absorption, so compression of pulse duration and repetition rate simultaneously. • Corresponding Q-switched pulsed laser performance are realized regulation and optimization by adjusting the ratio of FO NPs to PI.

Passively Q - Switched Linear Cavity IR Fibre Laser via Nonlinear Polarization Rotation

Abstract: Setup for self-starting passive Q-switch operation of IR fibre laser via nonlinear polarization rotation (NPR) was demonstrated for the first time for linear cavity. A Q-switched pulse duration of ~ 600 ns, a maximum peak power of ~16 W and an average power of 408 mW have been obtained at 223 kHz repetition rate for 5.1 W pump power from 1319 nm CW Nd: YAG laser launched to ~ 2.78 m unidirectional single-clad Tm-doped silica fibre linear cavity using only flat polarizer and feedback mirror to induce NPR. The dependence of the fibre laser output characteristics on the polarization angle of the polarizer is also reported. However, self induced passive Q-switching in linear fibre laser cavities is only observed in fibres with angled cleaved ends and with lengths that are around the optimum length for CW operation. Keywords: IR fibre laser, Passive Q-switching, Nonlinear polarization rotation, Linear cavity, Ring cavity. PACS: Fiber lasers, 42.55.Wd, Q-switching, 42.60.Gd.