Excimer laser has important applications in integrated circuit lithography, materials processing, medicine, and scientific research due to its short wavelength and high pulse energy. However, there remains a big gap in the high-end excimer laser technology between China and the international advanced level. In this article, the characteristics and development history of excimer lasers were briefly introduced first. Second, the development status and requirements of the excimer laser technology and its related typical applications were analyzed in China and abroad. Third, the main issues of the development of domestic excimer laser technology were proposed. Finally, in view of the relevant problems and needs, it is suggested that in the future, more efforts should be made to deepen the research, including basic generic technology research (design, preparation, and characterization of high-performance and high-end deep UV components, basic theory and verification research of discharge dynamics, etc.); long pulse, high repetition rate, and high energy/power technology; as well as emerging or potential application fields and derivative technologies, so as to lay the foundation for the independent and controllable development of excimer lasers in China.

A multikilowatt all-fiber amplifier with narrow spectral linewidth is investigated by using commercial 20/400 μm active fiber due to its more extensive application prospects. Stimulated Brillouin scattering (SBS) is suppressed effectively by combining multiple approaches including optimizing linewidth-broadened seed, shortening fiber length, and a counterpumped configuration. Consequently, the output power is pushed up to 3.01 kW with M2=1.17, and the linewidth is maintained at 48 GHz. The detailed characteristics of SBS are presented and analyzed in the frequency and time domains as output power is gradually raised. A high optical-to-optical efficiency is obtained with 85.6% and amplified spontaneous emission is reduced to 40 dB with respect to a laser signal. The proposed architecture reaches a relatively high output power with excellent beam quality under the condition of the equivalent linewidth for the commercial 20/400 μm active fibers in robustly all-fiberized structures.

光纤是光导纤维的简称,通常是一种圆柱形的光波波导.它利用全反射的原理把光波约束在纤芯,并引导光波沿着光纤轴线方向传输.用石英玻璃代替铜线改变了世界. 光纤作为一种传导光波的介质,自1966年被高锟提出以来,凭借其通信容量大、抗干扰能力强、传输损耗低、中继距离长、保密性能好、适应能力强、体积小、重量轻、原材料来源丰富等优点被广泛应用.被人们称为“光纤之父”的高锟也因此获得了2009年的诺贝尔物理学奖.随着光纤性能的日趋完美和实用化,光纤对电信行业的变革产生了革命性的推动,它已经基本取代铜线成了现代通信中的核心组成部分.

Accurate and precise wavelength controlling of narrowband excimer lasers is essential for the lithography of an integrated circuit. High-precision wavelength tuning and calibration of a line-narrowed ArF laser are presented in this work. The laser spectrum is narrowed to a sub-picometer with a line narrowing system. Absolute wavelength calibration of the line-narrowed laser is performed based on the optogalvanic (OG) effect using iron hollow cathode discharge (HCD). An sccuracy of better than 0.1 pm for wavelength tuning and calibration is achieved with our homemade wavemeter.

The effect of laser energy density on the light-trapping structures of amorphous silicon (alpha-Si) thin films is studied both theoretically and experimentally. The thin films are irradiated by a frequency-doubled (lambda = 532 nm) Nd:YAG pulsed nanosecond laser. An effective finite difference time domain (FDTD) model is built to find the optimized laser energy density (E-L) for the light trapping structures of alpha-Si. Based on the simulation analysis, it shows the variation of reflection spectra with laser energy density. The optimized reflection spectra at E-L = 1000 mJ/cm(2) measured by UV-visible spectroscopy confirms to agree well with that corresponding to the depth to diameter ratio (h/D) in the FDTD simulation. The surface morphology characterization by optical microscope (OM) and scanning electron microscope (SEM) accords fairly well to of light-trapping modeling in the simulation. (C) 2016 Elsevier Ltd. All rights reserved.

We report on a spectral beam combination of five narrow-linewidth fiber amplifiers. The five-channel output beams are combined in both the near and far field using a polarization-independent diffraction grating that mainly preserves the beam quality of the individual amplifiers. Each amplifier contains a two-stage preamplifier and a main amplifier delivering about 240 W of optical power, which allows a total combined output power of 1.23 kW with an efficiency of over 95%.

The effect of laser energy density on the crystallization of hydrogenated intrinsic amorphous silicon (a-Si:H) thin films was studied both theoretically and experimentally. The thin films were irritated by a frequency-doubled (λ = 532 nm) Nd:YAG pulsed nanosecond laser. An effective density functional theory model was built to reveal the variation of bandgap energy influenced by thermal stress after laser irradiation. Experimental results establish correlation between the thermal stress and the shift of transverse optical peak in Raman spectroscopy and suggest that the relatively greater shift of the transverse optical (TO) peak can produce higher stress. The highest crystalline fraction (84.5%) is obtained in the optimized laser energy density (1000 mJ/cm2) with a considerable stress release. The absorption edge energy measured by the UV-visible spectra is in fairly good agreement with the bandgap energy in the density functional theory (DFT) simulation.

A Dammann grating is used as a spatial filter for a passive coherent beam combination (CBC) of three Yb-doped fiber amplifiers with an all-optical feedback loop. Using this diffractive-optics-based spatial filtering technique, we demonstrate CBC with 20 W output power, and the visibility of the far-field interference pattern is up to 88.7%. Measurements suggest that this approach is robust with respect to laboratory environment perturbations, and it can scale to high powers and large arrays.

A typing error in our manuscript is reported and corrected. (C) 2014 Optical Society of America

A passive coherent beam combination of three nanosecond Yb-doped fiber amplifiers by an all-optical feedback loop is realized by a Dammann grating intracavity spatial filter. By using this diffractive-optics-based spatial filtering technique, three tile-aperture laser beams are phase-locked with a peak power of 1.02 kW. The width of the combined pulses is 9.6 ns, and the repetition frequency is 2.208 MHz. The visibility of the far-field interference pattern is up to 82.9%. The results show that this approach can scale to larger arrays and higher powers.

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text J. Zhou, B. He, Y. Yang, H. Liu, Y. Zheng, and Q. Lou, "Dammann-grating-based Passive Coherent Beam Combining by an All-optical Feedback Loop," in International Photonics and OptoElectronics Meetings, OSA Technical Digest (online) (Optica Publishing Group, 2014), paper FTh3E.1. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

A Dammann-grating-based aperture filling technology is demonstrated in a passive coherent beam combination fiber amplifier array, which is phase-locked using an all-optical feedback loop. The maximum output power is 206 W. The combined efficiency of a three channels aperture filling is discussed and demonstrated to vary with the output power. Perturbative factors leading to the loss of the combined efficiency are theoretically simulated and the key factor is the residual phase error. Theoretical and experimental results show that this technology has good potential to achieve higher brightness in a single beam.

The beam quality factor M2 of multimode fiber lasers using coiling technique is studied based on the fiber bend loss theory. M2 is obtained through calculating bend loss and intensity change of different modes in a multimode fiber. The influence of bend-induced field deformation on M2 is evaluated. Relationship of M2 to coiling radius is studied for the multimode fiber lasers. It is shown that M2 keeps almost unchanged in some range of the coiling radius. The performance of mode selection is compared between fibers with the same V-parameter but different NA values. Fibers with smaller NA value are shown to be more effective for mode selection and are more conducive to achieving good beam quality laser output.

A linearly-polarized, high peak power, short-pulse, Q-switching Yb-doped large-mode-area photonic crystal fiber (PCF) oscillator with three-level system operation is demonstrated. By optimizing cavity parameters and adopting linear polarization component, the laser can easily obtain linearly-polarized output over 2 W at 978 nm with polarization extinction ratio (PER) up to 43 dB without any additional wavelength filter. Less than 50 ns stable output pulses are achieved within repetition range of 10 kHz-200 kHz and short pulse of 9 ns pulse duration, 130 kW peak power at 10 kHz can be reached. The characteristics and the key issues of the laser, such as interpulse ASE, spectrum ASE around 1030 nm, are with detailed discussion in the paper.

Theoretical simulation and experiments based on a prism beam expander and an echelle grating are conducted to study the dependence of linewidth and pulse energy on incidence angle and slit width. With a larger prism incident angle or narrower slit width, the linewidth becomes narrower while the laser pulse energy becomes lower. However, the pulse energy can be improved by optimally designing the prism beam expander. In addition, a subpicometer linewidth ArF laser is obtained with a double-prism beam expander and an echelle grating.

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text J. He, S. Du, Z. Wang, Z. Wang, J. Zhou, and Q. Lou, "5 MHz High-Repetition-Rate Acousto-optic Q-Switched photonic crystal fiber laser operating at 978 nm," in Advanced Solid-State Lasers Congress, G. Huber and P. Moulton, eds., OSA Technical Digest (online) (Optica Publishing Group, 2013), paper ATu3A.06. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

The effect of laser energy density on the crystallization of hydrogenated amorphous silicon (a-Si:H) thin films was studied theoretically and experimentally. The thin films were irritated with a frequency-doubled (λ=532 nm) Nd:YAG pulsed nanosecond laser. An effective finite element model was built to predict the melting threshold and the optimized laser energy density for crystallization of intrinsic amorphous silicon. Simulation analysis revealed variations in the temperature distribution with time and melting depth. The highest crystalline fraction measured by Raman spectroscopy (84.5%) agrees well with the optimized laser energy density (1000 mJ/cm2) in the transient-state simulation. The surface morphology of the thin films observed by optical microscopy is in fairly good agreement with the temperature distribution in the steady-state simulation.

An injection-locked fiber laser is introduced to the passive fiber laser coherent beam combination with all-optical feedback loop. A coherent beam combining system with two-dimensional four Yb-doped fiber amplifier chains is established, and the injection-locked fiber laser works as a switchable seed source. The 1064 nm output laser of the injection-locked fiber laser is extinguished automatically as the feedback injection power is high enough, and the injection-locked fiber laser acts as an amplifier for the feedback laser with 7.4 dB gains. We find that the phase-locked far-field interference pattern of our system with seed laser extinguished is stable, and the visibility is up to 91.5%, which is slightly higher than the prevalent method with auxiliary seed laser (88.2%).

We demonstrate a passive coherent beam combination of two nanosecond amplifiers by using an all-optical feedback loop. An electro-optic amplitude modulator is utilized to tune the pulse width and the pulse repetition frequency of combined laser pulse. The positive correlation between the visibility of far-field coherent patterns and the pulse duty ratio is found. The range of tunable pulse repetition frequency is from 2.023 MHz to 6.069 MHz, and the range of tunable pulse width is from 10 ns to 50 ns. The maximum visibility is up to 85%. This approach presented here provides a promising way for power scaling of high power nanosecond fiber laser and maintaining beam quality simultaneously.

We report a high-peak-power, single-polarized master oscillator power amplification system employing polarization- maintaining Yb-doped rod-type photonic crystal fiber. The MOPA system comprises of a Q-switched microchip laser generating ~630ps pulses at 8.6 kHz repetition-rate and two amplification stages employing double cladding fiber and rod-type PCF respectively. The MOPA system obtains narrow spectral bandwidth, single-polarized pulses of 9W maximum output average power, corresponding to peak power of 1.7MW.