Tunable graphene Q-switched erbium-doped fiber laser with suppressed self-mode locking effect

Self-mode locking effect in a wideband tunable graphene-based passively Q-switched erbium-doped fiber laser has been observed experimentally. Q-switching is achieved by using graphene as a saturable absorber, while a tunable bandpass filter with a narrow bandwidth is used to obtain wideband tunability. We propose to suppress the modulation on each pulse from self-mode locking by introducing three subring resonators constructed with three 3 dB couplers into the laser ring cavity. Moreover, the laser output characteristics with respect to pump power are studied in detail. A stable Q-switched erbium-doped fiber laser with a tunable range from 1522 nm to 1568 nm is demonstrated experimentally.     

Wideband tunable Q-switched fiber laser using graphene as a saturable absorber

An ultra-wide wavelength tuning range, which covers three different band regions consisting of the S-, C-, and L-bands, is proposed and demonstrated for a graphene-based Q-switched erbium-doped fiber laser using a tunable bandpass filter as the wavelength tuning and filtering mechanism. A 3?m length of erbium-doped fiber is used as the gain medium in a ring laser cavity configuration, with absorption coefficients of between 11 and 13 dB?m^?1 at 980?nm and about 18?dB?m^?1 at 1550?nm. The tuning range of the Q-switching pulses covers a wide wavelength range of 58?nm, which spans from 1512.5?nm to 1570.5?nm. In addition, the lasing and Q-switching thresholds are considerably low, with respective values of ～11.0?mW and ～18.4?mW. A repetition rate of 55.3?kHz is obtained at the maximum pump power of 100.4?mW, together with pulse width and pulse energy of 1.6?μs and 25.8?nJ, respectively.     

Triple-wavelength passively Q-switched ytterbium-doped fibre laser using zinc oxide nanoparticles film as a saturable absorber

We report on the generation of a triple-wavelength passively Q-switched ytterbium-doped fibre laser using a saturable absorber (SA) based on zinc oxide nanoparticles (ZnO NPs) film. The SA was fabricated by embedding ZnO NPs powder into a polyvinyl alcohol as a host polymer. By properly adjusting the pump power and the polarization state, single-, dual- and triple-wavelength Q-switching are stably generated without additional components (such as optical filter, or fibre grating). For the triple wavelength operation, the fibre laser generates a maximum pulse repetition of 87.9 kHz with the shortest pulse duration of 2.7 μs. To the best of authors’ knowledge, it’s the first demonstration of triple-wavelength passively Q-switching fibre laser using ZnO NPs as a SA. Our results suggest that ZnO is a promising SA for multi-wavelength laser operation.     

Q-switched 2-micron lasers by use of a Cr2+:ZnSe saturable absorber

Flash-lamp-pumped Ho:YAG (2090-nm) and Tm:YAG (2017-nm) lasers were, for the first time to our knowledge, passively Q switched by use of a Cr(2+):ZnSe saturable absorber. A Q-switched Ho laser with 1.3-mJ pulse energy and ~90-ns pulse duration and a Q-switched Tm laser with ~3.2-mJ pulse energy and 90-ns pulse duration were demonstrated. Compared with the free-running output energies at the Q-switching threshold pump levels, the Q-switching efficiencies were approximately 5% for the Ho:YAG laser and 16% for the Tm:YAG laser.     

Comparison study of CsLiB6O10 and beta-BaB2O4 as nonlinear media for optical parametric oscillators

We compare the relative merits of the new nonlinear materials CsLiB6O10 and beta-BaB2O4 for use as gain media in a singly or doubly resonant pulsed optical parametric oscillator pumped by a Q-switched Nd:YAG laser with various parameters. Angle tuning or a wide range can be theoretically stimulated under type I and type II(1) critical phase matching for CsLiB6O10 crystal. The tunable range is 237-2775 nm; the range was extended to the ultraviolet wavelength by fifth-harmonic generation in CsLiB6O10. A comparison of the tunable ranges, resonant thresholds, and conversion efficiencies of CsLiB6O10 and beta-BaB2O4 is obtained by computer simulation. We verify that CsLiB6O10 is an excellent ultraviolet crystal.     

High-Repetition-Rate Q-Switched Diode-Pumped Nd:YAG Laser at 1.444 mum

A diode-pumped Q-switched Nd:YAG laser that operates at the eye-safe 1444 nm wavelength has been developed. When pumped by a 10-W fiber-coupled array at 808 nm, it generated 1 W in cw operation and 560 mW at 20-kHz repetition rate with active Q-switching. Design issues such as thermal lensing characterization and beam quality are discussed.     

宽带可调谐光源瞬时波长测量方法研究

激光波长作为“米”基准的重要实现途径之一，其量值准确性在计量校准、精密测量以及光谱探测等领域具有十分重要的意义。目前基于标准物质吸收谱线的波长基准仅能用于单一波长的计量校准，对于宽带光源波长校准手段有限。本文开展宽带连续调谐激光波长校准技术研究，利用飞秒激光频率梳宽光谱、光频可溯源至原子频率标准、稳定性高的特点，对宽带调谐光源在调谐输出时的连续光波长进行测量，最终实现了1 nm带宽下可调谐激光器调谐输出过程中瞬时值的测量，并利用该结果对可调谐激光器在121 GHz带宽的调频非线性度进行了评价。     

Tunable laser diode system for noninvasive blood glucose measurements

Optical sensing of glucose would allow more frequent monitoring and tighter glucose control for people with diabetes. The key to a successful optical noninvasive measurement of glucose is the collection of an optical spectrum with a very high signal-to-noise ratio in a spectral region with significant glucose absorption. Unfortunately, the optical throughput of skin is low due to absorption and scattering. To overcome these difficulties, we have developed a high-brightness tunable laser system for measurements in the 2.0-2.5 microm wavelength range. The system is based on a 2.3 microm wavelength, strained quantum-well laser diode incorporating GaInAsSb wells and AlGaAsSb barrier and cladding layers. Wavelength control is provided by coupling the laser diode to an external cavity that includes an acousto-optic tunable filter. Tuning ranges of greater than 110 nm have been obtained. Because the tunable filter has no moving parts, scans can be completed very quickly, typically in less than 10 ms. We describe the performance of the present laser system and avenues for extending the tuning range beyond 400 nm.     

Flash-lamp-excited self-injection-seeded Q-switched Ti:Al(2)O(3) laser oscillator

A self-injection-seeded, flash-lamp-excited, Q-switched laser oscillator is presented. The laser comprises two resonators that are operated sequentially. The first resonator, which includes all the high insertion loss, damage prone, wavelength tuning, and line-narrowing components, is used to generate the seed signal. The second resonator is a low-loss, Q-switched resonator whose output wavelength and line width are controlled by the seed signal. Output pulses of energy as high as 325 mJ have been obtained that are tunable over a range of the order of 90 nm and with a bandwidth of the order of 0.05 nm.     

Performance of diode-end-pumped Cr, Nd:YAG self-Q-switched and Nd:YAG/Cr:YAG diffusion bonded lasers

Self-passively Q-switching of a diode-pumped Cr,Nd:YAG, where the Cr⁴⁺ is used as a saturable absorber for the 1064 nm laser emission is reported. The maximum average output power was obtained using an output coupler of R=86%. The self-Q-switched diode pumped laser yielded 1.86-W average output power with low threshold pumping power (≈1.7-W), average slope efficiency of ≈34%, pulse duration of about 14–16 ns, and modulation frequency ranging from 2.4 to 73 kHz, depending on the input pumping power. These results are the highest reported for self-Q-switched lasers. Higher slope efficiency (42%) and shorter Q-switched pulses were obtained for a Q-switched Nd:YAG/Cr⁴⁺:YAG diffusion bonded laser. A comparison of the codoped Cr,Nd:YAG laser performance, with that of a diffusion bonded laser is reported and analyzed.     

All-solid-state tunable DCM dye laser pumped by a diode-pumped Nd:YAG laser

Lasing is observed near 620 nm in a DCM dye doped TiO(2)-content organically modified silicate (ORMOSIL) pumped by frequency-doubled radiation from a diode-pumped Q-switched Nd:YAG laser. The laser wavelength is tunable over 60 nm. A conversion efficiency of 18% is obtained at its central wavelength of 621 nm. The laser output energy has only a 10% reduction after 27,000 pulses at a pump repetition rate of 30 Hz and a pump intensity of 1 J/cm(2). An all-solid-state, compact, long-lifetime, and tunable dye laser has been demonstrated.     

Laser and Fluorescence Properties of Organic Dye DCM Doped Sol-Gel-Derived Solid-State Materials

1.IntroductionSol-gelprocessingoffersanewandeasyap-proachforproducingthermallysensitivedyedopedsolid-statematerialswithgreaterhomogeneityandhighconcentrationofdyemoleculesataroundroomtemperaturel1'2].Inthepastdecades,therehavebeenmanyreportsonsolid-statedyelasersbasedonpoly-merandsol-gelsl3~6l.Althoughencouragingprogresshasbeenachievedindyedoped1asersbasedonpoly-mermaterials,lowthermoconductivityandlaserdam-agethresholdarestillthemaindefectsofpolymerdyelasers.Recentadvancesinsol-gelOrmosilhav…     

The effect of passive Q-switching observed in an erbium-doped fiber laser at a low pumping power

The effect of passive Q-switching was observed in an erbium fiber laser at a pumping power below 100 mW. The phenomenon is explained by a cascade process of the Rayleigh light scattering and the induced Mandelshtam-Brillouin scattering in a fiber resonator of the laser. In the Q-switched mode, the laser produced giant output pulses with a duration below 15 ns, a peak power up to 200 W, and a repetition period of 300–500 μs. The proposed Q-switching mechanism is inferred from the characteristic features of the laser pulse oscillograms measured at a ∼1 ns resolution. Previously, this effect was observed only in high-power fiber lasers at a pumping power of ∼2 W.     

Efficient acousto-optic Q switching of Er:YSGG lasers at 2.79-microm wavelength

A flash-lamp-pumped Er:Cr:YSGG laser at 2.79-mum wavelength has been acousto-optically Q switched. The Q-switched pulse energy and duration depend on pump pulse level and relative Q-switching time. Limits of single-pulse operation with the given acousto-optic diffraction efficiency have been determined. Resonator length, position of the Q switch, and output mirror reflectivity have been varied to obtain high pulse energy and the shortest pulse duration in the TEM(00) transverse laser mode. A maximum single-pulse energy of 27 mJ and a minimum pulse duration of 120 ns were obtained with an output mirror reflectivity of approximately 25%. The highest Q-switched single-pulse energy amounted to 52% of the free-running, fundamental mode output pulse energy.     

Nickel oxide nanoparticles thin film saturable absorber for 1-micron pulsed all-fibre lasers operation

A passive Q-switched and mode-locked ytterbium-doped fibre laser (YDFL) pulse generation using a nickel oxide thin film as a saturable absorber is reported. The nickel oxide nanoparticle thin film was fabricated by a simple processing technique, and it has a modulation depth of 39% and saturation intensity of 0.04 MW/cm². The saturable absorber was constructed by inserting a small piece of the film between two fibre ferrules. Then it was integrated in a YDFL cavity. The Q-switching operation started at a threshold pump power of 117.73 mW with an initial wavelength of 1073.5 nm. When the pump power was raised from 117.73 to 133 mW, the repetition rate grew from 9.5 to 15.8 kHz. The pulses had a maximum pulse energy of 478 nJ. Furthermore, a stable self-started mode-locked pulse was also succesfully generated at the threshold pump power of 97.3 mW. The central wavelength and repetition rate of the laser were 1037.72 nm and 23 MHz, respectively. The maximum pulse energy of 0.56 nJ and a peak power of 26.4 W were recorded at a pump power of 137.5 mW.     

Low-threshold, single-frequency, coupled cavity Ti:sapphire laser

A novel coupled resonator was developed for narrow-bandwidth, tunable, solid-state lasers. Stable, single-longitudinal-mode, gain-switched titanium:sapphire pulses were obtained across a 130-nm operating range limited by the cavity optics. The low threshold fluence of 0.7 Jcm(-2) makes the cavity attractive for other tunable laser media, particularly when gain is low or parasitic loss is high. A model has been developed that can be used to predict the mode structure of the coupled cavity and for optimization at specific wavelength regions.     

Intracavity pumped nanosecond optical parametric oscillator emitting in the eye-safe range

We report on a 1.57-mum wavelength singly resonant optical parametric oscillator (OPO) using a noncritically phase-matched KTP crystal intracavity pumped by an electro-optically Q-switched Nd:YAG laser. A simple model for numerical calculation of the temporal profile of the laser and signal pulses developed inside the intracavity pumped OPO (IPOPO) resonator is described. Working conditions for single-pulse and multipulse parametric oscillation are established. A single signal pulse of 8.1-mJ output energy was obtained when the laser was pumped three times above the pulsed IPOPO threshold. A pulse duration of 5.9 ns was measured at 1.5 times above threshold for the IPOPO.     

Single-nanowire single-mode laser

We demonstrate single-mode laser emission in single nanowires. By folding a 200 nm diameter CdSe nanowire to form loop mirrors, single-mode laser emission around 738 nm wavelength is obtained with line width of 0.12 nm and low threshold. The mode selection is realized by the vernier effect of coupled cavities in the folded nanowire. In addition, the loop structure makes it possible to tune the nanowire cavity, opening an opportunity to realize a tunable single-mode nanowire laser.     

Q-switched fiber lasers with carbon nanotubes hosted in ceramics

Q-switched fiber ring lasers operated by single-walled carbon nanotubes (SWNTs) hosted in SiO(2) matrix are demonstrated by highlighting their stable operation and dramatically improved thermal damage threshold. Employing aerosol deposition process, SWNTs are incorporated into the ceramic host at room-temperature without solubility limitation. After experiencing the intracavity optical power higher than 15.3 dBm, the hosted SWNTs survive to provide Q-switching operation. The continuous repetition rate tuning is achieved in the range of 11.1-32.2 kHz with the pulse-duration of 7.1-15.8 μs at 1558.5 nm.     

Performance improvement in a directly 879 nm dual-end-π-polarized-pumped CW and pulsed GdVO₄/Nd:GdVO₄ laser

A continuous-wave and Q-switched 10 kHz GdVO?/Nd:GdVO? laser by 879 nm laser-diode pumping was demonstrated. We combined dual-end-π-polarized-pumping, half-wave plate (HWP) insertion, composite laser crystals, and dual Q-switching techniques to obtain a 1.06 μm nanosecond laser with high temporal and spatial quality. A polarization beam splitter was used to divide the unpolarized pump beam into two linearly polarized beams to increase the absorption efficiency. The output performance was improved obviously by inserting a HWP into the cavity. The pulse duration was compressed and the peak power was increased for a doubly Q-switched laser, in contrast to a single acousto-optical Q-switched laser under the same conditions.