新颖的中红外6.45μm激光医疗应用及光源研究进展(特邀)

基于新型激光消融/切除机理,中红外6.45μm激光用于生物组织消融/切除时不但效率高,而且附带损伤仅为微米量级,其附带损伤区域与细胞尺寸相当,是目前附带损伤最小的激光刀技术,在精准医疗领域具有重要应用前景。文中对低附带损伤6.45μm激光消融/切除机理、生物医学应用及6.45μm激光国内外研究现状进行了综述,并对其发展前景进行了展望。

6.45μm激光加热浮法玻璃后温度分布特性研究

为了提升激光可控断裂法切割玻璃的质量,研究了6.45μm激光照射浮法玻璃后材料的温度变化。利用激光输出的连续功率计算了6.45μm激光照射玻璃后的温度分布,并通过实验验证了该模型的正确性;模拟对比了相同激光参量下6.45μm激光和10.6μm激光加热玻璃后的温度场,通过实验获得了光滑、无表面裂纹的切割样品。结果表明,6.45μm激光产生的表面温度低于10.6μm激光;6.45μm激光可以利用热裂法获得高质量切割端面。该研究对中红外激光玻璃切割的模型建立和方案优化具有一定的帮助。

Thulium laser treatment for bladder cancer

Recent innovations in thulium laser techniques have allowed application in the treatment of bladder cancer.Laser en bloc resection of bladder cancer is a transurethral procedure that may offer an alternative to the conventional transurethral resection procedure.We conducted a review of basic thulium laser physics and laser en bloc resection procedures and summarized the current clinical literature with a focus on complications and outcomes.Literature evidence suggests that thulium laser techniques including smooth incision,tissue vaporization,and en bloc resection represent feasible,safe,and effective procedures in the treatment of bladder cancer.Moreover,these techniques allow improved specimen orientation and accurate determination of invasion depth,facilitating correct diagnosis,restaging,and reevaluation of the need for a second resection.Nonetheless,large-scale multicentre studies with longer follow-up are warranted for a robust assessment.The present review is meant as a quick reference for urologists.

In vitro comparison of the vaporesection of human benign prostatic hyperplasia using 70-and 120-W 2μm lasers

The purpose of the current ex vivo study was to compare the speed of vaporesection of human prostatic tissue with benign prostatic hyperplasia （BPH） and the depth of tissue damage using 70- and 120-W 2-tim laser devices. Fresh prostatic tissue specimens were obtained from five patients by open prostatectomy, and were divided into separate groups （70 and 120 W） based on the energy of the laser output （70 and 120 W, respectively）. The vaporesection speed, coagulation zone depth and the necrotic tissue layer in the prostatic tissue were evaluated. The current result showed that the speeds （mean±s.d.） of vaporesection were 5.21±0.66 and 10.39±1.15 g/5 min for the 70 and 120 W groups, respectively （P=0.000）. There was no difference in the depth of necrosis/ coagulation （0.98±0.1310.30±0.09 and 0.99±0.12/0.31±0.08 mm） for the 70 and 120 W groups, respectively. In conclusion, both 70- and 120-W 2μm laser devices had superficial tissue damage during the vaporesection of human prostate tissue; moreover, the 120-W laser offers a higher vaporesection speed than the 70-W laser.

Observation and optimization of 2 μm mode‐locked pulses in all‐fiber net anomalous dispersion laser cavity

We integrally demonstrate 2μm mode-locked pulses performances in all-fiber net anomalous dispersion cavity.Stable mode-locking operations with the center wavelength around 1950–1980 nm can be achieved by using the nonlinear polarization rotation structure and properly designing the dispersion management component.Conventional soliton is firstly obtained with a total anomalous dispersion cavity.Due to the contribution of commercial ultra-high numerical aperture fibers,net dispersion is reduced to-0.077 ps2.So that stretched pulse with 19.4 nm optical bandwidth is obtained and the de-chirped pulse-width can reach 312 fs using extra-cavity compression.Under pump power greater than 890 mW,stretched pulse can evolve into noise-like pulse with 41.3 nm bandwidth.The envelope and peak of such broadband pulse can be compressed with up to 2.2 ps and 145 fs,respectively.The single pulse energy of largely chirped stretched and noise-like pulse can reach 1.785 nJ and 1.53 nJ,respectively.Furthermore,extra-cavity compression can also contribute to a significant increase of peak power.

An Innovative Gas Sensor with On-Chip Reference Using Monolithic Twin Laser

An innovative gas sensor with on-chip reference using a monolithic twin laser is proposed. In this sensor a monolithic twin laser generates two closer laser beams with slight different wavelengths alternatively, one photodiode is used to catch both absorption and reference signals by time division multiplexing. The detection of nitrous oxide adopting this scheme using a 2.1 I^m antimonide laser and an InGaAs photodiode has been demonstrated experimentally with detection limit below i ppm. Using this on chip reference scheme the fluctuations from the optical path and devices can be compensated effectively; the sensor system is simplified distinctly.

Low noise,continuous-wave single-frequency 1.5-μm laser generated by a singly resonant optical parametric oscillator

We report a low noise continuous-wave （CW） single-frequency 1.5-μm laser source obtained by a singly resonant optical parametric oscillator （SRO） based on periodically poled lithium niobate （PPLN）. The SRO was pumped by a CW single-frequency Nd：YVO4 laser at 1.06μm. The 1.02 W of CW single-frequency signal laser at 1.5 μm was obtained at pump power of 6 W. At the output power of around 0.75 W, the power stability was better than ±l.5% and no mode-hopping was observed in 30 min and frequency stability was better than 8.5 MHz in 1 min. The signal wavelength could be tuned from 1.57 to 1.59 μm by varying the PPLN temperature. The 1.5-μm laser exhibits low noise characteristics, the intensity noise of the laser reaches the shot noise limit （SNL） at an analysis frequency of 4 MHz and the phase noise is less than 1 dB above the SNL at analysis frequencies above 10 MHz.

MXene Ti_3C_2T_x saturable absorber for pulsed laser at 1.3 μm

The excellent optical properties of MXene provide new opportunities for short-pulse lasers. A diode-pumped passively Q-switched laser at 1.3 μm wavelength with MXene Ti3C2Tx as saturable absorber was achieved for the first time. The stable passively Q-switched laser has 454 ns pulse width and 162 kHz repetition rate at 4.5 W incident pumped power. The experimental results show that the MXene Ti3C2Tx saturable absorber can be used as an optical modulator to generate short pulse lasers in a solid-state laser field.

High-Power Single-Spatial-Mode GaSb Tapered Laser around 2.0 μm with Very Small Lateral Beam Divergence

We report high-power single-spatial-mode type-I GaSb-based tapered lasers fabricated on the InGaSb/AlGaAsSb material system. A straight ridge and three different tapered waveguide structures with varying flare angles are fabricated to optimize the output power and spatial-mode performance. The best devices exhibit single-spatial-mode operation with room-temperature output power up to 350？mW in continuous-wave mode at an emission wavelength around 2.0？μm with a very small far-field lateral divergence angle, which is beyond state of the art in terms of single-spatial-mode output power.

Spectral and laser properties of Yb and Ho co-doped(YLa)_2O_3 transparent ceramic

Highly transparent Yb,Ho doped（YLa）2O3 ceramic was fabricated by conventional ceramic processing with nanopowders.The absorption and emission spectra of the ceramic was investigated.The energy transfer mechanism between Yb3＋ and Ho3＋ was also discussed.The strong emission band around 2 μm indicated that the Yb-Ho：（Y 0.90 La 0.10）2O3 transparent ceramic is a promising gain medium for the generation of 2 μm laser emissions.The laser operation of Yb-Ho co-doped（YLa）2O3 ceramic at 2.1 μm is first reported.

MICROSTRUCTURE IN LASER FUSED HIGH SPEED STEEL W6Mo5Cr4V2(M2)

Microstructure of the deepest zone of high speed steel W6Mo5Cr4V2(M2)melt after laser fu-sion was found to be so fine as the ehill zone of a solidified ingot.When narrower chill zoneformed,the long columnar dendrites grow into the melt and then the fine equiaxed cellularstructure appears in upper melt region nearly surface.The substructure of cellular grains anddendrites was observed to consist of martensite and retained austenile,while the carbides asM_6C_■ Cr_7C_3 and MC distributed at their boundaries.It is believed that the highermicrohardness up to HV_(0.1)=865-960 of the laser fused structure of the alloy is due to the oc-currence of martensite.

Optimization of High Power 1.55-μm Single Lateral Mode Fabry-Perot Ridge Waveguide Lasers

Optimization of the high power single-lateral-mode double-trench ridge waveguide semiconductor laser based on InGaAsP/InP quantum-well heterostructures with a separate confinement layer is reported. Two different waveguide structures of Fabry-Perot lasers emitting at a wavelength of 1.55 μm are fabricated. The influence of an effective lateral refractive index step on the maximum output power is investigated. A cw single mode output power of 165mW is obtained for a 1-mm-long uncoated laser.

Synchronously Pumped Mode-Locked 1.89 μm Tm-Doped Fiber Laser with High Detuning Toleration

We propose and demonstrate a synchronously pumped mode-locked Tm-doped fiber（TDF） laser without any extra mode-locking elements. Pumped by a 1.56 μm pulse fiber laser, the TDF laser generates 1.17 ps pulses with a spectral width of 9.7 nm and a repetition rate of 9.33 MHz. The emission wavelength is tunable along with the cavity length detuning in a wide range of 3 mm. The high detuning toleration is beneficial to achieve high temperature and vibration stability in all-fiber configuration lasers.

Progress of optically pumped GaSb based semiconductor disk laser

This paper reviewed the development of optically pumped GaSb based semiconductor disk lasers （SDLs） emission at 2 μm wavelength region from the aspects of wavelength extending, power scaling, line-width narrowing and short-pulse generation. Most recently, the wavelength of GaSb based SDLs has been extended to 2.8 μm. The highest output power of the GaSb based SDLs has been reached to 17 W at the temperature of 20 ℃. By using active stabilization, the GaSb based SDL with line-width of 20 kHz and output power of 1 W was realized. Moreover, the shortest pulse obtained fromthe GaSb based SDLs was generated as short as 384 fs by incorporating semiconductor saturable absorber mirrors（SESAM） in the cavity.

Structure Character of M-A Constituent in CGHAZ of New Ultra-Low Carbon Bainitic Steel under Laser Welding Conditions

800 MPa grade new ultra-low carbon bainitic （NULCB） steel is the recently developed new generation steel. The microstructure in the coarse-grained heat affected zone （CGHAZ） of NULCB steel under laser welding conditions was investigated by thermal simulation. The influence of the cooling time from 800℃ to 500℃.t8/5 （0.3-30 s）, on the microstructure of the CGHAZ was discussed. The experimental results indicate that the microstructnre of the CGHAZ is only the granular bainite which consists of bainitic ferrite （BF） lath and M-A constituent while t8/5 is 0.3-30 s. The M-A constituent consists of twinned martensite and residual austenite, and the change of the volume fraction of the residual austenite in the M-A constituent is very small when t8/5 is between 0.3 and 30 s. The morphology of the M-A constituent obviously changes with the variation of t8/5.As t8/5 increases, tile average width, gross and shape parameter of the M-A constituent increase, while the line density of the M-A constituent decreases.

Techniques trend analysis of propagating laser beam quality measurement

Different methods of measuring a propagating laser beam quality are summarized.The disadvantages in traditional way in measuring a laser beam quality is analyzed and the insufficiencies of the Shack-Hartmannin method which is commonly using wave front technique at present is pointed out.Finally,the transmission intensity equation based(TIE-based)measuring way in a laser beam quality evaluation and the corresponding advantages are discussed,which is believed to be a deve-l oping trend in laser beam evaluation.

Experimental Stu dies of 374μm ^(15)NH_(3) Optically Pumped Far-Infrared Laser

374μm far-infrared raliation of ^(15)NH_(3) pumuped by CO_(2) laser has been studied experineutally.The fficiecncy of p11 alosorption of the pounp bean.stability of the output power aund freqpeuey were exiuined in detail.Fur the plurpose of applixution in the plasi1n diagnostirs,n copurisou with 432μm of the formic acid laser was also carried out..

Holmium Oxide Film as a Saturable Absorber for 2μm Q-Switched Fiber Laser

This work reports on the use of the holmium oxide （Ho2O3） polymer film as a saturable absorber （SA） for generating stable Q-switching pulses operating in a 2μm region in a thulium-doped fiber laser cavity. The SA is prepared by diluting a commercial Ho3O2 powder and then mixing it with polyvinyI alcohol （PVA） solution to form a Ho2O3-PVA film. A tiny part of the film about 1mm×1 mm in size is sandwiched between two fiber ferrules with the help of index matching gel. When incorporated in a laser cavity driven by a 1552-nm pump, stable Q-switching pulses are observed at 1955nm within the pump power range of 363 491 roW. As the pmnp power increases within this range, the repetition rate rises from 26 kHz to 39 kHz, as the pulse width drops from 4.22μs to 2.57μs. The laser operates with a signal-to-noise ratio of 47dB, and the maximum output power and the pulse energy obtained are 2.67mW and 69ng, respectively. Our results successfully demonstrate that the Ho2O3 film can be used as a passive SA to generate a 2μm pulse laser.

Diode-End-Pumped Tm:Ho:GdVO_(4) Microchip Laser at Room Temperature

Room-temperature Tm:Ho:GdVO4 microchip laser operated around 2μm is demonstrated for the first time to our knowledge.At a heat sink temperature of 283K,maximum output power of 29.7m W is obtained by using a 0.25-mm-long crystal at an absorbed pump power of 912mW,corresponding to a slope efficiency of 5.0%.At the temperature to 283K,a single-longitudinal-mode laser as much as 8mW at 2048.5 nm is achieved.The M^(2)factor is measured to be 1.4.

Progress of 1.5～1.6 μm Laser Crystals

Eye-safe 1.5～1.6 μm lasers have important applications in optical fiber communication, medicine, laser-range-finding, lidar, etc. Er^3＋ and Yb^3＋ co-doped crystal pumped by diode laser around 976 nm is an attractive method for obtaining 1.5～1.6 μm laser in compact device with high output beam quality. In this paper, the recent research and progress of several important Er^3＋ and Yb^3＋ co-doped laser crystals at 1.5～1.6 μm in authors’ lab are reported.