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Using a YVO4/Nd:YVO4/YVO4 composite crystal end pumped by laser diode, we demonstrate the simultaneously Q-switched and mode-locked self-Raman laser at the firststokes wavelength of 1176.07 nm. Its corresponding linewidth was measured to approximately be 0.14 nm. At the pump power of 38 W and the pulse repetition frequency of 50 kHz, the maximum average output power at 1176 nm was obtained to be 1.34 W with the corresponding optical conversion efficiency of 3.6%. The highest pulse energy and the highest peak power were obtained to be 35 μJ and 10.5 kW, respectively. The shortest mode-locked pulse width of the laser was obtained to be ~300 ps with the corresponding repetition rate of mode-locked laser pulse is ~ 1.11 GHz

We theoretically and numerically investigated the modal properties of three different kinds of cross-section rotating mirrors. At the same facet size, the fundamental frequency of equilateral-triangle cross-section rotating mirror (ET-RM) was 8725.4 Hz, which was 1.81 times and 4.60 times higher than that of equilateral-square and equilateral-hexagonal rotating mirrors. The displacement response curves of the three kinds rotating mirrors show that the amplitude of the first peak is further larger than the second one. The first bending modal of rotating mirror is the main reason of the damage for rotating mirrors. The maximum working speed of ET-RM with face size of 17.32 mm × 36 mm is 44,400 rpm. That of the other two kinds of rotating mirror are 37,800 rpm and 27,000 rpm respectively. The equilateral-triangle cross-section as an ideal structure of rotating mirror for ultra-high-speed cameras based on the dynamic properties.

A simple Mach–Zehnder interferometer (MZI) was presented for high temperature measurement. The device was composed of a short segment of suspended-core fiber (SCF) sandwiched between two standard single mode fibers (SMFs) with a misaligned splicing joint. Lower temperature measurements were firstly carried out from room temperature to 190 °C, and the obtained sensitivity at the wavelength of 1465 nm was 25.82 pm/°C. However, a nonlinear response was further achieved for high-temperature sensing up to 1000 °C. Between 20 and 200 °C, the sensitivity was just 24.24 pm/°C at the wavelength of 1457 nm, whereas a higher sensitivity of 53.87 pm/°C was acquired in the range of 200–1000 °C. In addition, the strain cross-sensitivity was extremely low. As a result, the device can be developed as a strain-independent temperature sensor and become an excellent candidate for high temperature measurement.

Rotating mirror is not only as an imaging element in optical path of ultra-high speed camera, where imaging quality is affected by surface quality and plane deformation of the rotating mirror, but also as an element to implement ultra-high speed, because performances of the ultra-high-speed camera system are mainly dependent on the static and dynamic mechanical properties of the rotating mirror. In this paper, the static and dynamic properties of magnesium alloy rotating mirror with equilateral-triangle cross-sections were investigated by theoretically and numerically method. At the speed of 2×105 rpm, the maximum lateral deformations of the mirror facet with width 17.32 mm and length 40 mm is 2.476 μm. The maximum von Mises stress is 35.1 MPa. The deformation and stress are less than that of aluminum alloy rotating mirror, which has been successfully applied in many types of RM for ultra-high speed cameras. The first three frequencies of magnesium alloy rotating mirror are 9,539.9 Hz, 9,540.9 Hz and 12,726.0 Hz, respectively. While the first three frequencies of aluminium alloy rotating-mirror are 9,683.9 Hz, 9,685.2 Hz and 11,016.0 Hz. From which it is preliminarily shown that a magnesium alloy rotating mirror can be used as replacement for an aluminium alloy rotating mirror in ultra-high-speed camera.

We demonstrate a novel and compact fiber-probe pressure sensor based on a micro-Fabry–Perot interferometer (FPI). The device is fabricated by splicing both ends of a short-section simplified hollow-core photonic crystal fiber (SHC-PCF) with single-mode fibers. Then, a microchannel is drilled by a femtosecond laser micromachining in the SHC-PCF to allow air to diffuse in. The pressure sensing mechanism is based on the dependence of the air refractive index on pressure. We use both theory and experiment to investigate the sensing characteristics. A micro-FPI with a length of 272 μm demonstrates a pressure sensitivity of 4.071 nm/MPa at 1580 nm and a low-temperature sensitivity of 1.1 pm/°C at atmospheric pressure. We further study the temperature cross sensitivity of the sensor under different pressures. The sensor also shows strong stability and good reversibility, and may be potentially used in pressure sensing applications.

In this letter, we reported long period fiber gratings (LPFGs) fabricated by femtosecond laser pulses direct writing in grapefruit microstructured fiber. The mode field distribution and dispersion property of this fiber was analyzed by finite-element method. Two LPFGs were fabricated with different periods of 230 and $250~\mu \text{m}$ , the resonant dips appeared at the wavelengths of 1325.8 and 1449.4 nm, respectively. In addition, sensing characteristics of the LPFG with the period of $250~\mu \text{m}$ were investigated in theory and experiment. The experimental results show that the strain and temperature sensitivities are 1.88 pm/ $\mu \varepsilon $ and 0.267 pm/°C, respectively. It indicates that the temperature cross sensitivity is as low as $0.142~\mu \varepsilon $ /°C.

A novel and simple sensor based on fiber-optic modal interferometer fabricated by a segment of low elliptical hollow-core photonic bandgap fiber for simultaneous temperature and twist measurements is demonstrated. Meanwhile the sensor can also measure the twist angle and determine the twist direction simultaneously. The mode distribution of EHC-PBGF is demonstrated both in theory and experiments. There is an obvious difference of two transmission dips on the temperature and twist. The twist sensitivities of Dip 1 and Dip 2 are obtained to be −31.95 and −585.8 pm/(rad/m), respectively. The temperature sensitivities are 12.99 pm/°C for Dip 1 and 5.09 pm/°C for Dip 2, respectively. Two parameters of twist and temperature can be distinguished and measured simultaneously by using a sensing matrix. Meanwhile the structure is found to be weakly sensitive to the axial strain. It has the advantage of avoiding the crosstalk of strain in the applications.

A high power diode-pumped continuous-wave Tm:YAP laser with a piece of silicon chip as the output coupler (Si-OC) is demonstrated. A maximum output power of 13 W with a beam quality of M2 ≤ 1.45 at 1931 nm was obtained, corresponding to an optical-to-optical efficiency of 31%, and a slope efficiency of 33%. To our best knowledge, this is the first report of utilizing silicon as a output coupler on solid Tm:YAP laser system. The mechanism of silicon output coupler on Tm:YAP laser is also discussed in this letter. Because of the intriguing characteristics of silicon, such as high damage threshold, low cost and long-pass filter property, double-sided polishing single crystal silicon chip can perform as a good output coupler in high power laser system near 2 μm region.

A diode-end-pumped composite YVO4/Nd:YVO4/YVO4 crystal self-Raman laser at the second-Stokes wavelength of 1,764 nm is demonstrated. The maximum average output power of second-Stokes radiation was up to 0.99 W at a pump power of 34 W and a pulse repetition frequency of 20 kHz, corresponding to an optical conversion efficiency of 2.9 %. The highest peak power and the shortest pulse duration were 21.5 kW and 1.92 ns, respectively.

Mach–Zehnder interferometer strain sensors made from pieces of photonic crystal fiber spliced to standard single mode fibers are fabricated with different lengths. High strain sensitivity of 2.1 pm/μe at 1550 nm is achieved with the length of 45 mm. The interference is induced by the core mode and the high order core mode due to the special air hole structure of PCF, which is independent of the surrounding refractive index. The temperature sensitivity (∼13.24 pm/°C) is relatively low. This structure is good in avoiding cross sensitivity in strain measurement and is fabricated with a simple process and low cost.

We report a diode-end-pumped acousto–optically Q-switched composite YVO4/Nd:YVO4/YVO4 crystal self-Raman yellow–green laser, based on the intracavity sum-frequency generation of the fundamental and first-Stokes fields in LiB3O5 crystal. Maximum average output power at 559 nm is 3.55 W at the incident pump power of 32 W and pulse repetition frequency (PRF) of 30 kHz, with an optical conversion efficiency of 11%. The highest pulse energy and peak power are 129 μJ and 10.5 kW at 20 kHz PRF, respectively. The power stability of yellow–green radiation is better than 2% for 40 min at an average output power around 3 W.

We reported the generation of visible red light through degenerate four wave mixing (FWM) in an all solid photonic bandgap fiber (PBGF), which was achieved by pumping the fiber with a 800 nm Ti:sapphire-based femtosecond pulse laser. At a fiber length of 30 m, a broadband anti-Stokes spectrum range from 620 nm to 740 nm was obtained at the highest pump power, the spectrum evolution as a function of pump power and propagation distance had been measured. Furthermore, the intensity-dependent parametric gain characteristic is also calculated, which accords well with the experimental results.

A method to characterize the thermal lens in a Nd:GdVO4 self-Raman laser is presented. The thermal focal length was measured to be as short as 180 mm with a self-Raman laser output power of 0.95 W. For comparison, the thermal focal lengths in the cases of fundamental operation and first-Stokes operation were measured experimentally, indicating that the heat generated in the SRS process exacerbated the thermal loading of the Nd:GdVO4 crystal.

We report a laser-diode-end-pumped acousto-optical Q-switched double-end diffusion-bonded Nd : YVO4 self-Raman laser at 1176 nm. The maximum average output power at the first-Stokes wavelength of 1176 nm was obtained to be 3.1 W at the incident pump power of 25 W and the repetition rate of 90 kHz, with the corresponding optical conversion efficiency of 12.4%. The shortest pulse width, the maximum pulse energy and the highest peak power were measured to be 5 ns, 42 μJ and 7.5 kW, respectively.

A laser diode pumped actively Q-switched Nd:GdVO4 self-Raman laser operating at 1173 nm is presented. The maximum output power was 2.26 W at an incident pump power of 18 W, with the corresponding optical conversion efficiency of 12.6%. Two different resonator configurations were investigated in order to achieve high output power and efficiency.

Supercontinuum generation (SC) of more than one octave spectrum spanning covering from 400 nm to 820 nm was achieved by pumping a piece of aluminum nitride (AIN) single crystal using a nanosecond 355 nm ultraviolet laser. The AlN with a thickness of ∼0.8 mm was grown by an optimized physical vapor transport technique and polished with solidification technology. Compared to previously reported ones, the achieved visible SC exhibited the broadest spectrum spanning from bulk materials pumped by a nanosecond pulse laser. The visible supercontinuum in AlN presents new opportunities for bulk material-based white light SC and may find more potential applications beyond typical applications in integrated semiconductive photoelectronic devices.

Femtosecond laser pulses with ultrashort time duration and ultrahigh peak power can cause the refractive index change in transparent materials and micron scale machining precision. Long period fiber gratings (LPFGs) with different periods and different grating lengths in the standard single mode fiber were fabricated, using laser direct writing method, by femtosecond laser pulses with pulse width of 200 fs at a center wavelength of 800 nm in air. The transmission spectra were studied in the range of 1510 nm to 1610 nm. Two LPFGs with period of 400 μm, and 550 μm, respectively fabricated with same irradiation power of 275 mW, were shown. The loss peak of 1552 nm, the transmission loss of 16 dB and the FWHM of 20 nm were obtained when the period of LPFG was 400 μm, while the loss peak of 1588 nm, the transmission loss of 20 dB and the FWHM of 25 nm were achieved when the period of LPFG was 550 μm. According to the theory of mode field coupling for long period grating, it was indicated that the modulation of refractive index Δn was in the level of 10-2.

A high-power continuous-wave (CW) all-solid-state Nd:GdVO4 laser operating at 1.34 μm is reported here. The laser consists of a low doped level Nd:GdVO4 crystal double-end-pumped by two high-power fiber-coupled diode lasers and a simple plane-parallel cavity. At an incident pump power of 88.8 W, a maximum CW output of 26.3 W at 1.34 μm is obtained with a slope efficiency of 33.7%. To the best of our knowledge, this is the highest output at 1.34 μm ever generated by diode-end-pumped all-solid-state lasers.

A novel and compact fiber-probe pressure sensor was demonstrated based on micro Fabry-Perot interferometer (FPI). The device was fabricated by splicing both ends of a short section simplified hollow-core photonic crystal fiber (SHCPCF) with single mode fibers (SMFs), and then a micro channel was drilled by femtosecond laser micromachining in the SHC-PCF to significantly enhance the pressure sensitivity. The pressure sensing characteristics based on micro-FPI have been investigated by measuring the signals through the demodulation of phase since the external signal imposing on the interferometer will induce the phase change of interference signal. Then a FBG was cascaded to demodulate the signal. A micro FPI demonstrates a maximum pressure sensitivity of 32 dB/MPa, while a low temperature cross-sensitivity of 0.27 KPa/°C. Hence it may have potential for pressure applications in harsh environment.

A long-period fiber grating (LPFG) was inscribed in suspended-core fiber by femtosecond laser. The LPFG was insensitive to surrounding refractive index, and the sensitivities to temperature and strain were 4.8 pm/°C and -1.65 pm/μϵ, respectively.

Low Nd-doped 0.3 at% Nd:GdVO 4 crystal with excellent crystal quality was grown by the Czochralski method. The maximum CW output power of 8.23 W was obtained when the 0.3 at% Nd:GdVO 4 crystal was pumped by a laser diode with power 27.9 W, giving the corresponding optical conversion efficiency of 29.5% and the average slope efficiency of 30.2%. The fracture-limited pump powers of different Nd-doped crystals were estimated.

We report a high-power laser-diode-array end-pumped 0.3 at. % Nd:GdVO4 continuous-wave laser operating at 1.34 μm. The maximum output power of 13.3 W was obtained at the incident pump power of 49.2 W, giving the corresponding optical conversion efficiency of 27% and the average slope efficiency of 28.5%. The thermal focal length of the Nd:GdVO4 crystal under the pump power from 15.3 to 50 W was measured experimentally.

Different Nd:Y x Gd 1 − x VO 4 mixed crystals with low Nd ion concentrations were successfully grown by the Czochralski method. The influences of different Gd/Y ratio on the Nd:Y x Gd 1 − x VO 4 mixed crystal properties were also investigated for the first time. X-ray powder diffraction (XRPD) results showed that the constants of a , c and the dimensions of unit cell were linear with the Gd content in mixed crystal. The thermal and optical properties show some interesting changes. The laser experiments have proved that Nd:Y x Gd 1 − x VO 4 crystals are new good laser materials.

A new liquid-phase method synthesizing Nd:GdVO 4 polycrystalline materials was introduced and excellent Nd:GdVO 4 single crystals were successfully grown by the Czochralski method. The effective segregation coefficients of Nd ion in Nd:GdVO 4 crystal were determined. The main defects and the methods of reducing them have been discussed. The fluorescence lifetimes of different Nd ions in crystal were also measured and found the crystal had obvious concentration quenching effect. In the field of high power laser system, a maximum laser output of 14.5 W at 1.06 μm was obtained, and the optical conversion efficiency is 63.0%. Up to 4.93 W laser output at 1.34 μm was also achieved with slope efficiency of 33.3%.

LD-pumped actively Q-switched intracavity frequency-doubled Nd:GdVO4/KTP red laser has been introduced. A maximum red average output power of 0.78 W at 671 nm was obtained at pulse-repetition frequency (PRF) of 15 kHz and the optical conversion efficiency was 6.5%. At the incident pump power of 12 W , the shortest laser pulse occurred at PRF of 15 kHz . Its full-width at half-maximum and the highest peak power were measured to be 35.8 ns and 3.38 kW . The largest single pulse energy of 56.3 μJ was achieved at PRF of 10 kHz . The influence factors on the Q-switched Nd:GdVO4/KTP red laser have been discussed.

This paper discusses a diode-laser-array end-pumped Nd:YVO4/BIBO green laser. Using a three-mirror folded cavity (V-shaped), a 1.06 W CW green output was obtained at an incident pump power of 8.5 W; the corresponding optical conversion efficiency was 12.5%. The relationship between the green output and the temperature of the BIBO crystal was investigated. The laser damage threshold of BIBO crystal was measured to be 600 MW cm−2 and 400 MW cm−2 at 1064 nm and 532 nm, respectively.

A Nd:GdVO 4 crystal was grown by the Czochralski method and the laser output at 1.34 μm was performed under the pumping source of laser diode (LD); up to 4.82 W laser output power at 1.34 μm was obtained. When a KTiOPO 4 (KTP) crystal was used as an intracavity frequency double crystal, red laser output at 671 nm up to 340 mW was obtained at room temperature.

We report continuous-wave (CW) and actively Q-switched laser performance achieved with an uncoated mixed laser crystal Nd:Lu 0.99 La 0.01 VO 4 at 1065.655 nm end-pumped by a laser-diode-array. The maximum CW output power of 6.26 W was obtained with the optical conversion efficiency of 31.3%. For the Q-switching operation, a maximum average output power of 6.06 W was obtained at the pulse repetition frequency (PRF) of 90 kHz, yielding an optical conversion efficiency of 30.3%. The highest pulse energy and highest peak power obtained were 954 μJ and 63.8 kW at the PRF of 5 kHz, respectively.

We demonstrated a diode-end-pumped continuous-wave and passively Q-switched Nd:GdVO 4 laser operating at 1.06 μm wavelength with a three-mirror folded resonator. The maximum continuous-wave output power of 8.18 W was obtained at the incident pump power of 22.5 W , with the corresponding optical conversion efficiency of 36.4%. For Q-switched operation, the maximum average output power was measured to be 4.64 W with the corresponding optical conversion efficiency of 25.8%, when the initial transmission of Cr 4+ :YAG crystal was 90%. The shortest pulse width of 83 ns , the largest pulse energy of 20.7 μJ and the highest peak power of 246.7 W were obtained when the Cr 4+ :YAG crystal with an initial transmission of 85% was used.

Intracavity type-I sum-frequency mixing of 1.06 μm and 532 nm with a (θ,ϕ)=(106°,77.2°)-cut YCOB crystal was performed in a compact laser-diode-pumped solid-state laser. Three type-II phase-matching KTP crystals with different length were used to generate 532 nm light by frequency-doubling of 1.06 μm . The 355 nm output power was measured with the three KTP crystals for Q-switched and continuous-wave (CW) operation, respectively. The maximum ultraviolet output power of 1305 μW was obtained with a 15 mm KTP crystal for CW operation, while the maximum ultraviolet average output power of 124 mW was obtained with a 10 mm KTP crystal for Q-switched operation.

A diode-end-pumped high-power Nd:GdVO 4 laser operating at 1.34 μm has been demonstrated. The maximum continuous-wave output power of 4.62 W was obtained at the incident pump power of 14.75 W, with the corresponding optical conversion efficiency of 31.3% and the average slope efficiency of 33.1%. By using the experimentally measured threshold pump power and slope efficiency, the stimulated emission cross-section of Nd:GdVO 4 crystal at 1.34 μm was determined to be 1.78×10 −19 cm 2 .

We have investigated the acousto-optically Q-switched intracavity second-harmonic generation of 1.06 μm in a 1.9-mm-long BiB3O6 crystal, cut for type-I phase-matching direction of (θ,ϕ)=(168.9°,90°), performed in a diode-end-pumped Nd:YVO4 laser. When the incident pump power was 4.3 W at 30 kHz of pulse repetition frequency, a maximum average green output power of 480 mW , the shortest pulse with FWHM width of 72 ns , the highest single pulse energy of 16 μJ and the maximum peak power of 222 W were obtained, giving the corresponding optical conversion efficiency of 11.2%. The effect of varying temperature in BIBO crystal on the average green output power was also investigated.

The transmission spectra of BiB 3 O 6 (BIBO) crystals are compared with KTP. With BIBO samples cut in different phase matching (PM) directions in (0 1 0) plane, we obtain efficient second harmonic generation (SHG) of pulsed laser radiation in this low symmetric crystal. For BIBO crystal, the direction (168.9°, 90°) exhibits a larger efficient nonlinear optical (NLO) coefficient than the direction (11.1°, 90°). For a 2.4 mm long, (168.9°, 90°)-cut BIBO, the SHG conversion efficiency can reach 67.7%, while at the same conditions the efficiency of a 4.7 mm long, (11.1°, 90°)-cut BIBO is 58% or so.

A long period fiber grating (LPFG) with resonance wavelength of 1335.76 nm was investigated, a twist sensitivity of 43.33 pm/(rad/m) against wavelength was obtained and its twist direction can be detected as well.

Efficient intracavity second-harmonic generation (SHG) has been realized in a new Li-doped GdCa4O(BO3)3 (GdCOB) crystal. 2.55 W CW SHG output power was obtained with an optical conversion efficiency of 19.6%, while the effective intracavity SHG efficiency was determined to be 44%. Compared to that of undoped GdCOB crystal, the effective SHG efficiency of the Li-doped GdCOB crystal was found to increase by 12.5%.

A diode-pumped acousto-optically Q-switched intracavity frequency-doubled Nd : GdVO 4 / KTP green laser formed with a flat–flat resonator was demonstrated. 3.05 W of average green output power at pulse repetition frequency (PRF) of 40 kHz was obtained with an optical conversion efficiency of 18.4%, the effective intracavity frequency-doubling efficiency was 57%. At the incident pump power of 15 W , the shortest laser pulse occurred at PRF of 25 kHz with FWHM width of 14 ns , yielding the highest peak power of 7.44 kW ; while the largest pulse energy of 0.14 mJ was achieved at PRF of 15 kHz .

An end-pumped acousto-optically Q-switched Nd:GdVO 4 laser has been demonstrated, from which 7.25 W average output power at 1.06 μm at pulse repetition frequency (PRF) of 60 kHz was obtained with an optical conversion efficiency of 38.1% and an averaged slope efficiency of 43.5%. At incident pump power of 17 W, the highest single pulse energy and peak power were achieved when the laser was operated at a PRF of 10 kHz, and were determined to be 340 μJ and 26.2 kW, respectively. The shortest laser pulse with FWHM width of 11 ns was observed at PRF of 20 kHz. Through intracavity frequency doubling, we obtained 2.18 W average green output power with pulse width of 45 ns at a PRF of 25 kHz, the corresponding optical conversion efficiency was 21.8%, and the resulting single pulse energy and peak power were determined to be 87.2 μJ and 1.94 kW, respectively. The results of theoretical calculations on the basis of rate equations are also presented, showing close consistency with the experimental data.

We report an intracavity frequency-doubled Q-switched self-Raman yellow laser at 587 nm. A composite Nd:YVO 4 crystal was utilized as self-Raman gain medium. The maximum average output power of yellow light obtained was 1.5 W at the incident pump power of 30 W and at a repetition rate of 50 kHz, corresponding to the optical conversion efficiency of 5%. The shortest pulse width, the maximum pulse energy and the highest peak power were measured to be 5.8 ns, 46.7 μJ and 5.9 kW, respectively.

Intracavity second-harmonic generation (SHG) at 1.06 μm in YCa 4 O(BO 3 ) 3 (YCOB) crystals cut for different type I phase-matching directions of (θ, ϕ)=(64.5°, 35.5°) and (33°, 9°) was investigated by employing an end-pumped Nd:YVO 4 laser formed with a three-mirror folded resonator. CW SHG output power of 2.35 W was obtained in the phase-matching direction of (64.5°, 35.5°) with an optical conversion efficiency of 18.1%, while the effective intracavity SHG efficiency was determined to be 42%. The intracavity SHG output was found to be insensitive to the varying temperature in YCOB crystal. The internal losses of YCOB crystal were measured to be 0.013 cm −1 .

High-power and high beam quality continuous-wave (CW) Nd:GdVO 4 lasers operating at 1.34 μm were experimentally demonstrated. The lasers consisted of either one or two crystals, which were both end-pumped by high-power fiber-coupled diode lasers. With one crystal, the maximum CW output power generated was 8.4 W. When two crystals were used, a maximum output power of 15.7 W was achieved with the incident pump power of 76.2 W, showing a slope efficiency of 26.2% and an optical-to-optical efficiency of 20.6%. The beam divergence at an output power of 15 W was measured to be about two times that of the diffraction limit.

A laser-diode-array end-pumped 0.3-at.% Nd-doped GdVO/sub 4/ high-power continuous-wave (CW) laser operating at 1.34 /spl mu/m has been demonstrated. The maximum CW output power of 8.23 W was obtained at the incident pump power of 27.9 W, giving the corresponding optical conversion efficiency of 29.5% and the average slope efficiency of 30.2%. Two Nd : GdVO/sub 4/ crystals with Nd/sup 3+/ concentration of 0.5 and 1.14 at.% were also investigated for the comparison to show the advantage of lowly Nd-doped crystals applied to high-power lasers.

We present a high power diode-pumped continuous-wave Tm:YLF (Tm3+-doped lithium yttrium fluoride) laser with apiece of silicon wafer as the output coupler (Si-OC laser) directly. Under the pump power of 40 W at 793 nm, a maximum output power of 12.1 W is obtained with a beam quality of M2 ≤ 1.55 at 1887 nm, corresponding to an optical-to-optical efficiency of 30.25% and a slope efficiency of 33.21%. To the best of our knowledge, this is the first report on directly utilizing silicon as an output coupler (Si-OC) in the solid Tm:YLF laser system. Due to the intriguing characteristics of silicon, such as negligible absorption in the wavelength region around 2 μm, high damage threshold, low cost and long-pass filter properties, double-side polished monocrystalline silicon wafer is considered as an outstanding candidate output coupler in the high-power laser system 2 μm spectral region, which may dramatically reduce the total manufacturing costs of the 2 μm laser system.

We have demonstrated a diode-end-pumped continuous-wave and Q-switched Nd:GdVO4 red laser through intracavity frequency-doubling with a type-II phase-matched KTP crystal. The maximum CW output power at 671 nm was measured to be 505 mW at the incident pump power of 12 W, with the corresponding optical conversion efficiency of 4.2%. When the repetition frequency was 15 kHz, the maximum quasi-CW red output power was obtained to be 781 mW, with the corresponding optical conversion efficiency of 6.5%, the shortest pulse width of 65 ns, the highest pulse energy of 52 µJ and the highest peak power of 801 W.

A high power diode-pumped composite YVO 4 /Nd:YVO 4 /YVO 4 actively Q-switched and mode-locked laser with ring resonator is demonstrated. For mode-locking operation, the maximum average output power at 1064 nm was up to 14.4 W at a pulse repetition frequency (PRF) of 85 kHz and at the incident pump power of 40 W, with the corresponding optical conversion efficiency of 36%. The shortest mode-locked pulse width was obtained to be 117.1 picosecond (ps) at the incident pump power of 26 W and PRF of 55 kHz, with the corresponding average output power of 7.37 W and the linewidth of 0.0436 nm. The highest pulse energy and peak power were obtained to be 93.5 μJ and 0.362 MW at PRF of 5 kHz and incident pump power of 40W, respectively.

Intracavity sum-frequency mixing of 1.06 μm and 532 nm in YCa4O(BO3)3 (YCOB) crystals cut for different type-I phase-matching directions of (θ,ϕ)=(106°,77.2°), (111°, 79.6°) and (65°, 82.8°) was investigated in a compact diode-end-pumped acousto-optical Q-switched Nd:YVO4/KTP laser formed with a three-mirror folded resonator. The maximum 355-nm average output power of 124 mW was obtained in the phase-matching direction of (106°, 77.2°) with a pump-to-ultraviolet conversion efficiency of 3.3% at the repetition frequency of 20 kHz.

We have fabricated a novel nanoweb fiber with web-like bundle of the fused-silica membranes with different thickness in its cross section. We pumped the 0.55-μm-thick membrane with 200-fs laser pulse at 800-nm just adjacent to its second-zero-dispersion wavelength, and demonstrated the polarization dependent visible supercontinuum (SC). The mode patterns were recorded in detail and analyzed at different polarization angles of incident pulse. The broadband spectrum range from ~350 nm to 950 nm is achieved for TM mode excitation. The tunable visible SC in the nanoweb fiber may be used in the substrate integrated waveguide for sensing.

A 30-mm-length YVO 4 /Nd:YVO 4 /YVO 4 composite crystal was used as self-Raman gain material. Yellow radiation at 587 nm was obtained by utilizing a 15-mm-length LBO as frequency-doubling crystal. The maximum average power at 587 nm is up to 8.05 W at the pulse repetition rate of 50 kHz and the pump power of 65 W, with the corresponding optical conversion efficiency of 12.38%. The shortest pulse width, the highest peak power and the maximum pulse energy were measured to be 5.57 ns, 22.1 kW, and 161 µJ, respectively.

Long period fiber gratings (LPFGs) with different periods in the standard single mode fiber were fabricated, using laser direct writing method, by femtosecond laser pulses with pulse width of 200 fs and the repetition rate of 250 kHz at a center wavelength of 800 nm in air. Comparative with bare LPFG in temperature sensor, LPFG had been encapsulated using large coefficient of thermal expansion of epoxy polymer and Aluminum to enhance the temperature sensitivity. The results showed that the temperature sensitivity of encapsulated LPFG was 2 times than that of bare LPFG. In addition, we also researched the relationship between resonant wavelength and surrounding refractive index (SRI) when LPFG immersed in refractive index of solution of different index at 20 degree Celsius.

We report, for the first time, efficient intracavity second-harmonic generation (SHG) at 1.06 μm in a non-linear optical crystal, BiB3O6 (BIBO), at a type-I phase-matching direction of (θ,ϕ)=(168.9°,90°), performed with a LD end-pumped cw Nd:YVO4 laser. A cw SHG output power of 364 mW has been obtained using a 1.9-mm-thick BIBO crystal. The optical conversion efficiency was 12.2% and the corresponding effective intracavity SHG efficiency was determined to be 32.4%. It was found that the intracavity SHG efficiency is greater than that obtained with a type-II phase-matching KTiOPO4 (KTP) crystal with a thickness of 3 mm. The effective non-linear optical coefficient (deff) ratio of BIBO to that of KTP, determined experimentally, is 1.23:1.

In this letter, LPFGs in standard telecommunication fibers without hydrogen loading were fabricated in air using laser direct writing method, by femtosecond laser pulses with pulse duration of 200 fs and output wavelength of 800 nm. The loss peak of 1430 nm, the transmission loss of 22.86 dB and the FWHM of 6.6 nm were obtained. Temperature dependence of wavelength shift in air was measured by placing the LPFG in a temperature chamber that is temperature controlled in the range of 70 -150 °C. The temperature sensitivities (uλ/uT) are estimated by using linearly regression fits, which was 43.2 pm/°C. The linearity of the temperature sensitivities is high and the R-squared values for uλ /uT is larger than 0.9979.