Employing external injection-locked Fabry-Perot laser scheme for mm-wave generation

We propose and experimentally investigate a 170 GHz band millimeter-wave source employing an external dual-mode-locked Fabry-Perot laser diode (FP-LD) with a 1.38 nm mode-spacing. Two continuous-wave (CW) lights are aligned to inject the corresponding modes of FP-LD to generate dual-beat-mode output. The proposed dual-mode laser is not only stable, but also has single-longitudinal-mode (SLM) output characteristics. Moreover, the relationship between two external-injected wavelengths is also analyzed for the dual-wavelength output.     

Tunable dual wavelength emission and bandwidth narrowing of a laser diode array with a simple external cavity

We report on the performance of a commercial, non-AR-coated diode laser bar of 20 W output power, consisting of 20 emitters, which uses an external cavity to achieve tunable, dual-wavelength emission. The separation between the wavelength peaks can be continuously tuned from 0 nm to 5 nm. An output power of 2.9 W is achieved at 3.7 nm peak-to-peak separation and higher powers are achieved for less separation. This is the highest dual wavelength output power reported so far using a standard diode laser array. PACS 42.55.Px; 42.60.-v; 42.60.Da; 42.60.Fc     

Generation of 10-GHz ultra-short pulses with low time jitter in an actively mode-locked fiber laser

We have experimentally achieved the 8.3-ps ultra-short pulse at 10 GHz repetition rate with the time jitter as low as 590 fs in an actively mode-locked fiber ring laser. The ring-cavity laser is mode-locked by a semiconductor optical amplifier based on cross-gain modulation. The external CW source is modulated with radio frequency signal by an amplitude modulator as the external optical pulses and, then, injected into the fiber ring cavity to achieve active mode locking. Further investigating the laser output characteristics, it indicates that the linewidth of employed CW source affects properties of the generated ultra-short pulse, such as phase noise and time jitter. Ultra-short pulse at high repetition rate with low time jitter can be generated by the optimization of CW laser source.     

Channel-switchable single-/dual-wavelength single-longitudinal-mode laser and THz beat frequency generation up to 3.6 THz

We propose and demonstrate a simple approach to realize channel-switchable single-/dual-wavelength single-longitudinal-mode (SLM) lasers and switchable beat frequency generation in the THz frequency regime. It is a compact fiber-ring laser incorporating a Fabry–Pérot etalon, tunable filters, and a piece of unpumped polarization maintaining erbium-doped fiber (PM-EDF) as the saturable absorber. Two parallel-arranged tunable filters are configured inside the ring cavity to support switchable dual-wavelength SLM operation and consequent THz beat frequency generation. Switchable 19-channel 200-GHz ITU-grid-compatible single-wavelength SLM operation is implemented. Moreover, the channel-switchable dual-wavelength SLM laser and switchable THz beat frequency generation ranging from 0.2 to 3.6 THz with a tuning step of 0.2 THz are demonstrated in the experiment.     

Robust diode-end-pumped Nd:GdVO4 laser passively mode-locked with saturable output coupler

Passively mode-locked diode-pumped solid-state (DPSS) Nd:GdVO₄ laser by using a saturable output coupler (SOC) in stable two-mirror linear cavity design is demonstrated. The laser was pumped by low-power single laser diode without any active cooling and external optics. Robust CW mode-locked operation was obtained with a repetition of 150–250 MHz, the pulsewidth was 12 ps, the lowest threshold for CW mode-locked was 185 mW. The optimal condition is found when the laser provides the set of characteristics: low CW mode-locking threshold (～260 mW), compact size (total cavity length 60 cm), good efficiency (～20%), and very stable output. At the output power of 270 mW an average power fluctuations within ±2% for long-term operation was obtained.     

Dual-wavelength external cavity laser with a sampled grating formed in a silica PLC waveguide for terahertz beat signal generation

We propose and demonstrate a dual-wavelength external cavity laser (ECL). In our design, a Fabry–Pérot laser diode (FP-LD) is hybrid-integrated with a sampled Bragg grating written in a silica planar lightwave circuit (PLC). The grating selects two laser wavelengths that share the same laser cavity. The dual-wavelength oscillation with a side mode suppression ratio >32 dB has been demonstrated experimentally. Experimental results indicate that the hybrid-integrated dual-wavelength ECL exhibits strong dual-wavelength emission corresponding to beat frequency of 1 THz. Simulations of this system also indicate good mutual coherence of the two modes and stability of the 1 THz beat signal. PACS 42.79.Dj; 42.60.By; 42.55.Px     

Yb:CaF2–YF3 transparent ceramics ultrafast laser at dual gain lines

Yb³⁺:CaF₂-YF₃ transparent ceramics with excellent optical quality was successfully fabricated by hot-pressed method. Pulsed laser properties of this ceramics were investigated for the first time. Laser diode (LD) was applied as the pump source to generate a dual-wavelength mode-locked (ML) laser. The maximum average output power was 310 mW, which represents the highest output power of ultrafast calcium fluoride ceramic laser. The spectrum separated at 1048.9 nm and 1049.7 nm with a total pulse duration of 8.9 ps. The interval period between the beating signals was about 4.3 ps, corresponding to a 0.23 THz beat pulse repetition rate. These results demonstrate its potential in producing dual-wavelength ultrashort pulses. These Yb³⁺:CaF₂-YF₃ ceramics with low-cost and short-preparation period are ideal candidate materials for ultrafast lasers.     

基于石墨烯的1 064 nm连续锁模超短脉冲激光器

介绍了利用沉积在增透镜上的石墨烯薄膜作为可饱和吸收体、808 nm激光二极管端面泵浦Nd∶YVO4晶体的1 064 nm连续锁模激光输出特性。采用W型折叠谐振腔结构,在808 nm泵浦功率为8.0 W时,有稳定的连续锁模脉冲输出,平均输出功率达到185 mW;当抽运功率增加到16.0 W时,获得了中心波长1 063.4 nm、脉冲宽度为518 fs、重复频率为66.7 MHz、最大平均输出功率为323 mW的百飞秒量级超短脉冲激光输出。实验结果表明:石墨烯具有优良的可饱和吸收性,在1 064 nm波段能够实现高功率、百飞秒量级连续锁模脉冲激光输出。     

Dual-wavelength bandwidth-narrowed output of a high-power diode laser using a simple external cavity

Using an external cavity consisting of an etalon and a mirror, dual-wavelength operation of a high-power broad-area multi-stripe diode laser is achieved. The reflection of the etalon is used as the output beam of the system. The free-running bandwidth of the laser diode is about 2.0 nm. At dual-wavelength operation, the bandwidth of each wavelength component is narrowed to about 0.07 nm, while the space between them is 1.65 nm, determined by the FSR of the etalon. We obtain an available dual-wavelength output power of 2.0 W at the drive current of 6.5 A. The power ratio of the components at two different wavelengths can be changed by changing the temperature of the diode laser. To tune the wavelength of the dual-wavelength output, the temperature of the laser diode and the tilt angle of the etalon are changed simultaneously PACS 42.55.Px; 42.60.Fc; 42.60.Da     

Efficient continuous-wave eye-safe region signal output from intra-cavity singly resonant optical parametric oscillator

We report an efficient continuous-wave (CW) tunable intra-cavity singly resonant optical parametric oscillator based on the multi-period periodically poled lithium niobate and using a laser diode (LD) end-pumped CW 1064 nm Nd:YVO₄ laser as the pump source. A highly efficiency CW operation is realized through a careful cavity design for mode matching and thermal stability. The signal tuning range is 1401-1500 nm obtained by varying the domain period. The maximum output power of 2.2 W at 1500 nm is obtained with a 17.1 W 808 nm LD power and the corresponding conversion efficiency is 12.9%.     

基于组合模理论设计的激光二极管阵列外腔

针对激光二极管阵列提出了"组合模"概念,计算了组合模的远场分布.每个组合模在远场的空间分布呈双瓣结构.基于激光二极管阵列组合模的远场分布特征,设计了离轴外腔反馈的激光二极管阵列.运用此装置所获得激光二极管阵列的远场分布有了明显变化.与自由运转的激光二极管阵列相比,离轴外腔反馈的激光二极管阵列远场宽度减少了4.3倍.在抽运电流为16 A时,测得输出激光的功率1.82 W,这相当于相同电流下自由运转激光器输出功率的79%.组合模理论不仅可以用来指导设计一维离轴外腔反馈激光二极管阵列,而且也可以用于设计二维离轴外腔反馈激光二极管阵列.二维离轴外腔反馈激光二极管阵列可以产生高功率,高光束质量输出的激光.     

Generation of coherent terahertz radiation by photomixing of dual-mode lasers

We have reviewed and discussed the generation of continuous-wave terahertz radiation by the photomixing of dual-mode lasers, which includes a multi-mode laser diode (LD), a dual-mode microchip laser, a monolithic dual-mode DBR LD, and a widely tunable dual-mode external cavity LD. It is demonstrated by several experiments that the beat frequency of a dual-mode laser is more stable than the original laser modes because of the common-mode rejection effect. We also suggest a novel scheme by which the optical beat is stabilized to less than 1 kHz and its frequency can be precisely determined as well.     

Switchable and tunable dual-wavelength ultrashort pulse generation in a passively mode-locked erbium-doped fiber ring laser

A simple switchable and tunable dual-wavelength passively mode-locked erbium-doped fiber ring laser based on nonlinear polarization rotation (NPR) effect is proposed and experimentally demonstrated. The NPR effect effectively induces wavelength- and intensity-dependent loss to readily implement stable dual-wavelength passively mode-locked operation. The wavelength switching and tuning of the dual-wavelength ultrashort pulse laser are achieved only by appropriately rotating the polarization controllers. The side-mode suppression ratio of the output pulse is larger than 41 dB over a wavelength-tuning range of 43.4 nm. Moreover, triple-wavelength ultrashort pulse can also be observed.     

500 nm continuous wave tunable single-frequency mid-IR light source for C-H spectroscopy

A computer controlled tunable mid-IR light source, based on single resonant difference frequency generation (DFG), is experimentally investigated. The DFG process is pumped by an external cavity tapered diode laser, tunable over a spectral range of 30 nm. Grating feedback to the single mode channel of the tapered diode narrows the spectrum and allows for tuning of the emitted spectrum in the range from 780 to 810 nm. The DFG process takes place intra-cavity in a high finesse diode pumped 1064 nm solid state Nd:YVO₄ laser cavity, using periodically poled LiNbO₃ as the nonlinear material. Based on this new approach, a tunable single-frequency output power exceeding 3 mW was obtained in the mid-IR tuning range from 2.9 to 3.4 ??m.     

All fiber tunable- or dual-wavelength Yb-doped fiber laser covering from dissipative soliton to dissipative soliton resonance

In this Letter, a simple and passively mode-locking Yb-doped all fiber laser using a nonlinear polarization rotation technique operating under dissipative soliton(DS) or dissipative soliton resonance(DSR) conditions is proposed, furthermore, using a combination of a bandpass filter and a Loyt filter, tunable single-wavelength or dual-wavelength operation under two different conditions is realized, respectively. The tunable single?wavelength DS laser has a 5 nm tuning range from 1029 to 1034 nm with a pulse width of 110 ps. The tunable single-wavelength DSR operation laser has a range of 4 nm. In-depth research on the mechanism of the con?version between DS and DSR is carried out. Particularly, under dual-wavelength DSR operation, the obtained step-like pulses consist of two rectangular pulses with different energies. This work could help give a deeper insight into normal dispersion pulses.     

有源耦合腔激光器锁模特性研究

本文在理论上首次发现有源耦合腔激光器的自启动锁模和时域调制特性,并对其进行了全面的分析和计算.对有源耦合腔激光器的自启动锁模机制和时域调制特性给予详尽的数值计算结果和清晰的物理图象解释,提出在有源耦合腔锁模激光器中可用连续泵浦源代替锁模泵浦源,而且有产生更短的光脉冲可能性.     

Compact 584-nm light source based on sum-frequency mixing of diode pumped Nd:YLF lasers

A dual-wavelength continuous-wave (CW) diode end-pumped Nd:YLiF₄ (Nd:YLF) laser that generates simultaneous laser action at the wavelengths 1047 and 1321 nm is demonstrated. A total output power of 350 mW for the dual-wavelength was achieved. Furthermore, intracavity sum-frequency mixing at 1047 and 1321 nm was then realized in a LBO crystal to reach the yellow-green range. We obtained a total CW output power of 34 mW at 584 nm.     

A 1550-nm linearly tunable CW single-mode external cavity diode laser based on a single-cavity all-dielectric thin-film Fabry–Pérot filter

A 1550-nm linearly tunable CW single-mode external cavity diode laser (ECDL) based on a single-cavity all-dielectric thin-film Fabry–Pérot filter (s-AFPF) is proposed and realized in this paper. Its internal optical components as well as their operation mechanisms are introduced first, and then its longitudinal mode output characteristic is theoretically analyzed. Afterwards, we set up the experimental platform for the output characteristic measurement of this tunable ECDL; under different experimental conditions, we execute accurate and real-time measurements for the output central wavelength, output optical power, output longitudinal mode distribution, and the line-width of the tunable ECDL in its tuning process. By summing up the optimal experimental condition from the measured data, we obtain the optimal tunable relevant parameters ECDL of the tunable ECDL has a linear mode-hop-free wavelength tuning region of 1547.203 nm-1552.426 nm, a stable output optical power in the range of 40 μW-50 μW, and a stable output longitudinal mode distribution of a single longitudinal mode with a line-width in the range of 100 MHz-150 MHz. This tunable ECDL can be used in environmental gas monitoring, atomic and molecular laser spectroscopy research, precise measurements, and so on.     

Periodic adjustment of the position of a laser beam spot on a semiconductor saturable absorber mirror in a passively mode-locked solid-state laser

A laser diode end-pumped passively mode-locked Nd:YVO₄ solid-state laser with a semiconductor saturable absorber mirror (SESAM), in which the intracavity laser beam spot on the SESAM can be adjusted periodically, is investigated. Inserting a rectangular prism (RP) into the laser cavity is a promising approach towards the goal of periodically moving the position of the focus spot of the intracavity pulse on the SESAM surface to avoid the long-time irradiation of the laser beam on the same position, thereby solving a series of problems caused by damage to the SESAM and greatly prolonging its usage life. The adjustment of the rectangular prism in the laser cavity does not break the stable continuous wave (CW) mode-locked condition. The laser generates a stable picosecond pulse sequence at 1064 nm with an output power of 3.6 W and a pulse width of 14 ps. The instabilities of the output power and the pulse width are 1.77% and 4.5%, respectively.     

INVESTIGATION ON 16 W ULTRAHIGH FREQUENCY CW MODE-LOCKED Nd: YAG LASER

The cavity configurations designing and the experimental results of a 200MHz CW actively mode-locked Nd:YAG laser are reported. Arid 26W CW output and 16W CW mode-locked output power were obtained at a single lamp pumped power of 3.5kW, with pulse duration 100 ps.