Superresolution imaging of DNA tetrahedral nanostructures in cells by STED method with continuous wave lasers

DNA tetrahedral nanostructures are considered to be uew nanocarriers because they can be precisely controlled and hold excellent penetration ability to the cellular membrane. Although the DNA tetrahedral nanostructure is extensively studied in biology and medicine, its behavior in the cells with nanoscale resolution is not understood clearly. In this letter, we demonstrate superrcsolution fluorescence imaging of the distribution of DNA tetrahedral nanostructures in the cell with a simulated emission depletion （STED） microscope, which is built based on a conventional eonfocal microscope and can t）rovide a resolution of 70 nm.

A Review on Fiber Lasers

After a half century of development, fiber laser has evolved from a concept to a great family penetrating into various fields of applications. This paper reviews the history and current development of fiber lasers, with topics covering both continuous wave and short pulse fiber lasers. Important issues such as the major rare earth dopants, fiber laser brightness, polarization effects, clad pumping technology, beam combination, mode locking and pulse shaping are discussed in this paper.

Diode-pumped Nd:Y_xGd_(1-x)VO_4 crystal continuous-wave laser

The diode-pumped Nd:YxGd1-xVO4 crystal continuous wave (CW) laser operating at 1.06 μm with a simple plane-concave cavity and a V-shaped folded cavity for intracavity frequency-doubling have been studied. With the incident pump power of 8 W, an output power (1.06 μm) of 3.4 W was achieved, giving an optical conversion efficiency of 42.5%. 884 mW of stable green radiation was generated with the incident pump power of 5.9 W, giving an optical conversion efficiency of 15%.

Er-doped fiber ring laser gyroscopes operating in continuous waves

A direction related polarizer was inserted into a ring laser cavity to eliminate one of the two eigen-modes as well as spatial hole burning of the gain medium in a bidirectional Er-doped fiber ring laser. Thus, a fiber ring laser gyroscope （FRLG） operating in continuous wave was demonstrated. A beat signal of over 30-dB noise was observed and a good linear relation between the beat frequency shift and cavity rotation rate was obtained.

Continuous-wave four-wave mixing with linear growth based on elect romagnetically dual induced transparency

Using Schrodinger-Maxwell formalism, we propose and analyze a continuous-wave four-wave mixing (FWM) scheme for the generation of coherent light in a six-level atomic system based on electromag-netically dual induced transparency. We derive the corresponding explicit analytical expressions for the generated mixing field. We find that the scheme greatly enhances FWM production efficiency and is also capable of inhibiting and delaying the onset of the detrimental three-photon destructive interference by choosing the proper decay rate in the second electromagnetically induced transparency (EIT) process. In addition, such an optical process also provides possibilities for producing short-wave-length coherent radiation at low pump intensities.

All-solid-state quasi-continuous-wave high power dispersion cavity tunable Ti:sapphire laser

An all-solid-state quasi-continuous-wave dispersion cavity tunable Ti：sapphire laser pumped by a laser diode pumped frequency-doubled Nd：YAG laser is reported. Using a dense flint glass prism as the dispersion element, a tuning range from 730 to 880 nm with the tinewidth of 3 nm and the pulse width of 17.2 ns was obtained. The maximum output power of this laser system was 5.6 W at 786.3 nm corresponding to an optical-to-optical conversion efficiency of 25.5% under the pump power of 22 W.

Highly efficient continuous-wave laser operation of laser diode-pumped Nd,Y:CaF_2 crystals

The effect of co-doping Y3＋ and the doping concentration of Nd3＋ on the spectroscopic properties and laser performance of Nd：CaF2 crystals are investigated systematically. For a 0.5% Nd：CaF2 crystal, the emission life- time at 1.06 μm increases from 18 to 361 μs by co-doping 10 at.% Y3＋, while the emission cross section increases to 4.27 × 10^-20 cm2 at 1054 nm. With a 10 at.% doping concentration of Y3＋, Nd, Y：CaF2 crystals concentrate emission bands that peak at 1054 nm with shoulders at 1063 nm, and FWHM at about 30 nm. A diode-pumped, highly efficient laser operation is obtained with 0.5% Nd, 1070 Y：CaF2 and 0.6% Nd, 1070 Y：CaF2 crystals, with slope efficiencies over 30% and 27%, respectively, and a maximum output power up to 901 mW.

Efficient multi-wavelength lasers made of Nd:GdLuAG crystal

Owing to the small differences between the cross-sections of the four emission peaks around 1.3 μm, an efficient four-wavelength synchronous launched laser is demonstrated using a Nd：Gd Lu AG crystal. The laser has no special resonator design. The maximum output power is 4.28 W, which corresponds to a conversion efficiency of 45.6%. For the Q-switching, the laser operated in dual-wavelength mode, and the single pulse energy is maintained at ～80 μJ. By calculating the population inversion density, multi-wavelength emission characteristics in both continuous wave and Q-switching lasers are discussed.

Room temperature continuous wave operation of 1.33-um InAs/GaAs quantum dot laser with high output power

Continuous wave operation of a semiconductor laser diode based on five stacks of InAs quantum dots （QDs） embedded within strained InGaAs quantum wells as an active region is demonstrated. At room temperature, 355-mW output power at ground state of 1.33-1.35 μm for a 20-μm ridge-waveguide laser without facet coating is achieved. By optimizing the molecular beam epitaxy （MBE） growth conditions, the QD density per layer is raised to 4 × 10^10 cm^-2. The laser keeps lasing at ground state until the temperature reaches 65 ℃.

Quadratic nonlinear response to 1.56-μm continuous wave laser in semi-insulating GaAs

The nonlinear photoresponse to a 1.56μm infrared continuous wave laser in semi-insulating （SI） galliu- marsenide （GaAs） is examined. The double-frequency absorption （DFA） is responsible for the nonlinear photoresponse based on the quadratic dependence of the photocurrent separately on the coupled optical power and bias voltage. The electric field-induced DFA remarkably affects the native DFA in SI GaAs. The surface electric field or the surface band-bending of SI GaAs significantly affects the magnitude variation of the Dhotocurrent and dark current

2277-W continuous-wave diode-pumped heat capacity laser

A high power continuous-wave （CW） diode-pumped Nd：YAG laser operated in heat capacity mode is demonstrated by use of two identical highly efficient diode-pumped laser heads placed in a plane-plane resonator. The laser heads are uniformly pumped with a five-fold symmetrical side-pumping configuration, and each head is able to output maximum output power of 2200 W at 808 nm. Under a total pump power of 4290 W, the output power of the laser at 1064 nm is up to 2277 W, corresponding to an optical-to-optical efficiency of 53.1%.

High-power high-brightness 2-μm continuous wave laser with a double-end diffusion-bonded Tm, Ho:YVO_4 crystal

This letter demonstrates an efficient high-power high-brightness 2-μm continuous-wave （CW） laser with double-end, diffusion-bonded Tm, Ho：YVO4 crystal cooled with liquid N2. The reduction in thermal stress in the composite Tm, Ho：YVO4 rod enabled the laser to achieve a laser output power of 23.4 W at 2.05 μm, which is 1.37 times higher than that of the non-composite Tm, Ho：YVO4 rod. The corresponding slope efficiency is 37.3% and the optical optical conversion efficiency is 35.4%. The beam quality M2 factor is about 1.85 at 20 W output level with circularly symmetric beam spot.

Transurethral dividing vaporesection for the treatment of large volume benign prostatic hyperplasia using 2 micron continuous wave laser

Background The safety and efficiency of transurethral laser resection of the prostate to treat benign prostatic hyperplasia have been verified. However, this method does still not manage large volume prostates efficiently. To tackle this problem, we have designed a method of ＂transurethral dividing vaporesection of prostate＂ using a 2 micron continuous wave laser. The aim of this study was to evaluate the safety and efficiency of this method in the management of large prostates （〉80 ml）.Methods In this study, 45 cases of benign prostatic hyperplasia with a median prostatic volume of （123.7±26.7） ml （range, 80.2-159.8 ml） were treated by the same surgeon under epidural anesthesia. During the surgery, superapubic catheters were needed, and saline solution was used for irrigation. First, the prostate was divided longitudinally into several parts from the bladder neck to the prostatic apex, and then gradually incised transversely chip by chip. Intraoperative blood transfusion rate, postoperative complications, maximum urinary flow rate, International Prostate Symptom Score and quality of life scores were recorded for statistical analysis using SPSS 16.0 software.Results Intraoperatively, no transurethral resection syndrome was observed, and no blood transfusions were needed.The resected prostatic chips were easily flushed out of the bladder through the resectoscope sheath without the use of a morcellator. Median vaporesection time was （95.0±13.2） minutes （range, 75-120 minutes）, and the median retrieved and removed prostatic tissue were （25.2±5.1） g （range, 15.5-34.7 g） and （75.4±16.4） g （range, 43.8-106.1 g）, respectively. Median catheter time and hospital stay were （3.3±0.9） days （range, 3-5 days） and （4.8±1.8） days （range, 3-9 days）, respectively. After a follow-up of 6 to 12 months, two patients had stress urinary incontinence and three had anterior urethral strictures. Satisfactory improvement was seen in maximum urinary flow rate, International Prostate Symptom Score and quality of life scores.Conclusions This study showed that 2 micron laser vaporesection is a safe treatment for benign prostatic hyperplasia patients with large prostates, and the method of ＂dividing vaporesection＂ may help improve both surgical efficiency and patient outcomes.

NUMERICAL SIMULATION OF THE TEMPERATURE FIELD IN A SOLDER BALL UNDER PULSED LASER AND ITS EFFECT ON THE VIBRATION OF THE SOLDER

The research presented here is focused on the vibration condition of a small volume solder solder ball,which is placed on the surface of a soldering pad and is exerted a pulse modulated continuous wave laser heat source. Finite element method is applied to analyzed the temperature field in the solder ball, and experi- ment is conducted to test the vibration. the results show that,that, the temperature field flucturates with the same frequency as that of the laser pulse, which in turn causes a forced vibration of the same frequency in the liquid solder ball.

Dual-Wavelength Continuous Wave Photoacoustic Doppler Flow Measurement

Photoacoustic Doppler flow measurement based on continuous wave laser excitation owns the merit of clearly presenting the Doppler power spectra.Extending this technique to dual wavelengths can gain the spectral information of the flow sample extra to the flow speed information.An experimental system with two laser diodes respectively operated at 405 nm and 660 nm wavelengths is built and the flow measurement with black and red dyed polystyrene beads is performed.The measured Doppler power spectra can vividly reflect the flow speed,the flow direction,as well as the bead color.Since it is straightforward to further apply the same principle to multiple wavelengths,we can expect this type of spectroscopic photoacoustic Doppler flow measurement will be developed in the near future which will be very useful for studying the metabolism of the slowly moving red blood cell inside microvessels.

Development and Demonstration of Australian First Working Sodium Guide Star Laser

The Australian first working sodium guide star laser system has been designed and developed for various astronomical and space-related applications. A completely diode-pumped pulsed system was developed initially followed by a largely fiber-based continuous wave (CW) system operating at 589 nm achieved through a unique wavelength conversion scheme by combining 1342 and 1050 nm through a sum frequency generation process. For the CW system, single-mode laser beams at both 1342 and 1050 nm are achieved from fiber-based seed oscillators and fiber amplifiers. The output power of ~25 W at 1342 nm is achieved from a single frequency fiber Raman amplifier. Output power up to 70 W at 1050 nm is achieved from a Yb-doped fiber pre-amplifier followed by a Yb-doped fiber power amplifier. For the sum frequency generation process, optimum focusing parameters are evaluated and determined. The CW system has generated more than 20 W output power at 589 nm, a circularly polarised beam with a good beam quality, spectral linewidth ≤ 2 MHz, and the laser output locked on the sodium D2 line at 589.159 nm. The system has been successfully demonstrated at EOS Space Research Centre, Mt Stromlo, Canberra, and become the Australian first working sodium guide star laser system.

Efficient stable simultaneous CW dual-wavelength diode-end-pumped Nd:YAG laser operating at 1.319 and 1.338 μm

An efficient, stable diode-end-pumped simultaneous continuous-wave （CW） dual-wavelength laser operating at 1.319 and 1.338 ttm in a Nd：YAG crystal has been demonstrated. A total output power of 6.3 W is achieved at an absorbed pump power of 15 W, with a slope efficiency of 43.5%. The instability of output power is less than 1%. With a type II critical phase-matched KTP crystal inserted into the cavity as frequency doubler, a maximum output power of 200 mW in red region is acquired. In addition, a sixwavelength laser operation at 1.319 μm, 1.338 μm, 1.356 μm, 659.5 nm, 669 nm, and 678 nm is observed.

High-power diode-end-pumped Tm:YAP and Tm:YLF slab lasers

Diode-end-pumped continuous-wave （CW） Tm：YAP and Tm：YLF slab lasers are demonstrated. The a- cut Tm：YAP and Tm：YLF slabs with doping concentrations of 4 at.-% and 3.5 at.-%, respectively, are pumped by fast-axis collimated laser diodes at room temperature. The maximum CW output powers of 72 and 50.2 W are obtained from Tm：YAP and Tm：YLF, respectively, while the pump power is 220 W, corresponding to the slope efflciencies of 37.9% and 26.6%, respectively.

Cavity enhanced absorption spectroscopy for N_2O detection at 2.86 μm using a continuous tunable color center laser

The cavity enhanced absorption technique is applied to N2O detection around 2.86 μm using a continuous-wave color center laser. A high-finesse triangular ring cavity is used in this technology. Transmission through the cavity is obtained by jittering the cavity-length with a piezo on one of the cavity mirrors. A minimum detectable absorption coefficient of 2 × 10-6 cm-1 is achieved with a mirror reflectivity of 99.24%, corresponding to a N2O detection limit of 600 parts per billion.

Multiwavelength CW source with precise 25-GHz channel spacing based on longitudinal mode-carving of supercontinuum

We experimentally demonstrate a novel multi-wavelength continuous wave (CW) optical source with precise 25-GHz spacing based on the longitudinal mode-carving of a supercontinuum (SC) spectrum. The CW light was modulated with a 10-Gb/s non-return zero (NRZ) format. The experimental results show that the multiwavelength CW optical source is promising for dense wavelength division multiplexing (DWDM) systems.