被动锁模光纤激光器中双波长脉冲的产生

报道了从一个典型的基于非线性偏振旋转被动锁模光纤激光器中产生双波长锁模脉冲的研究。双折射诱导的波长相关腔传输使得激光器能同时在2个或多个波长上振荡,本文设计的激光器中最多有3个波长同时产生。由于偏振相关隔离器(PDI)引入的另外偏振相关腔损,通过调节偏振控制器(PC),3个波长中的任意2个能同时共振,并同时锁模。此外,双波长脉冲中2个不同波长的脉冲会相互作用,并通过交叉相位调制形成各种各样的调制格式。     

Simultaneous generation of wavelength tunable two-coloredfemtosecond soliton pulses using optical fibers

Wavelength tunable two-colored femtosecond (fs) soliton pulse generation is proposed and demonstrated for the first time, using passively mode-locked fs fiber laser and polarization maintaining fibers. The wavelengths of the two soliton pulses can be changed arbitrarily by varying the power and polarization direction of the fiber-input pulse. Ideal two colored soliton pulses in which the pulsewidths are about 200 fs are generated in the wavelength region of 1.56-1.70 μm for 110-m fiber. The generated pulses are almost transform-limited ones     

Theoretical and experimental study of pulse-amplitude-equalizationin a rational harmonic mode-locked fiber ring laser

A simple technique, based on nonlinear polarization rotation, for the amplitude equalization of high repetition rate pulses generated from a rational harmonic mode-locked fiber ring laser was demonstrated. Amplitude equalized pulses at 10 GHz (the fourth rational harmonic) were obtained with a harmonic component suppression ratio up to 30 dB. A theoretical explanation was given in detail, which indicates that, after pulse amplitude equalization, the situation of unequal pulse spacing can be improved to a certain extend     

Characterization of ultrashort pulse formation in passivelymode-locked fiber lasers

Pulse formation in an all-solid-state passively mode-locked neodymium glass fiber laser is investigated by employing characterization techniques in the time, optical, and radio-frequency domains. The pulses are generated by a combination of passive amplitude modulation arising from nonlinear polarization evolution and passive frequency modulation due to quasi-soliton-like pulse shaping. Several distinct operation modes for ultrashort pulse generation are described and pulses as short as 38 fs are directly generated in the cavity     

Complete characterization of ultrashort pulse sources at 1550 nm

This paper reviews the use of frequency-resolved optical gating (FROG) to characterize mode-locked lasers producing ultrashort pulses suitable for high-capacity optical communications systems at wavelengths around 1550 nm, Second harmonic generation (SHG) FROG is used to characterize pulses from a passively mode-locked erbium-doped fiber laser, and both single-mode and dual-mode gain-switched semiconductor lasers. The compression of gain-switched pulses in dispersion compensating fiber is also studied using SHG-FROG, allowing optimal compression conditions to be determined without a priori assumptions about pulse characteristics. We also describe a fiber-based FROG geometry exploiting cross-phase modulation and show that it is ideally suited to pulse characterization at optical communications wavelengths. This technique has been used to characterize picosecond pulses with energy as low as 24 pJ, giving results in excellent agreement with SHG-FROG characterization, and without any temporal ambiguity in the retrieved pulse     

调Q锁模类噪声方波脉冲掺铒光纤激光器

对基于非线性偏振旋转技术的L波段掺铒被动锁模光纤激光器中产生调Q锁模类噪声方波脉冲进行了实验研究。该类型脉冲中调Q包络内部包含的脉冲是基频方波,通过自相关迹证实该方波为类噪声脉冲。为了容易实现类噪声方波脉冲输出,将一段250 m普通单模光纤引进激光腔内。适当调节腔内的偏振控制器和泵浦功率,获得了基频为778.21 kHz的连续波锁模类噪声方波脉冲和由3.81 kHz可调谐到9.01 kHz的重复频率,单个调Q包络最高能量为1.06 J的调Q锁模类噪声方波脉冲。研究结果有利于进一步理解被动锁模光纤激光器中类噪声脉冲和调Q锁模的机理和特性。     

FM and AM mode locking of the homogeneous laser--Part I: Theory

A new general analysis for mode-locked operation of a homogeneously broadened laser with either internal phase (FM) or amplitude (AM) modulation is presented in this paper. In this analysis, a complex Gaussian pulse is followed through one pass around the laser cavity. Approximations are made to the line shape and modulation characteristics to keep the pulse Gaussian. After one round trip, a self-consistent solution is required. This yields simple analytic expressions for the pulse length, frequency chirp, and bandwidth of the mode-locked pulses. The analysis is further extended to include effects of detuning of the modulator, in which case analytical expressions are obtained for the phase shift of the pulse within the modulation cycle, the shift of the pulse spectrum off line center, the change in pulse length, and the change in power output. Numerical results for a typical Nd:YAG laser are given. In the case of the FM mode-locked laser it is found that there is a frequency chirp on the pulse and that this causes pulse compression and stretching when the modulator is detuned. Etalon effects and dispersion effects are also considered.     

波长可调的ps超短腔染料激光器的研究

本文报道了用锁模磷酸盐玻璃激光的倍频光泵浦若丹明B超短腔染料激光器的实验装置和实验结果,用TPF和OSA的组合装置研究了磷酸盐玻璃激光器的最佳运转条件,得到了脉宽～5ps的锁模脉冲系列,以此ps光源泵浦的染料激光器获得了波长为620.1～641.6nm,脉冲宽度小于4ps的单模可调谐激光输出。     

被动锁模光纤激光器的多模式输出

被动锁模光纤激光器腔体结构简单,可以实现全光纤集成,是产生超短脉冲的有效方法,而非线性偏振旋转又是其中最重要、最简单的被动锁模方法。为了研究基于非线性偏振旋转被动锁模光纤激光器存在的多种不同工作模式,采用实验方法,得到了包括正常孤子态,多脉冲束缚态,噪声像脉冲态等输出模式。结果表明,基于非线性偏振旋转被动锁模光纤激光器存在多种不同的工作模式。     

78 fs被动锁模掺Er3+光纤激光器

用性能稳定的976 nm激光二极管(LD)作为抽运光源,利用非线性偏振旋转(NPR)作为可饱和吸收体,实现了环形腔结构的被动锁模掺Er3 光纤激光器.在抽运功率为57 mW时,通过调节与波长无关的全光纤在线偏振控制器,获得了谱线宽度为40.8 nm,中心波长1544.0 nm,脉冲宽度为78 fs的稳定飞秒脉冲激光,其重复频率为11.18 MHz,平均输出光功率为5.4 mW,单个脉冲能量为0.5 nJ,峰值功率为6200 W.     

Tunable Raman Soliton Source Using Mode-Locked Tm–Ho Fiber Laser

We report a femtosecond pulse source that uses a mode-locked Tm-Ho oscillator and a self-frequency shift of Raman solitons in Tm-Ho power amplifier. The master oscillator mode-locked by an antimonide-based saturable absorber mirror produces 750-fs transform-limited soliton pulses over the tuning range from 1912 to 1972 nm. The soliton self-frequency shift in the amplifier resulted in transform-limited pulses with the wavelength adjusted by varying the amplifier pump power. We obtain ~150-fs soliton pulses at the wavelength of 2150 nm with average power up to 230 mW corresponding to the peak power of 27 kW. The efficiency of Raman conversion ranges from 47% to 62% over the tuning range     

重复率光泵染料锁模的研究

采用短谐振腔结构,利用分辨率10ps时间扩展器研究了染料浓度、流速与泵浦能量对锁模脉宽的影响。在重复率10～20次/S下,得到稳定的锁模脉冲输出。没有观测到卫星脉冲与失锁现象。脉冲幅度起伏优于10％。     

Experimental investigation on evolution of a split multi-wavelength bright-dark pulse in a mode-locked thulium-doped fiber laser

We report the experimental observation of evolving phenomenon of a split multi-wavelength bright-dark pulse in the nonlinear amplifying loop mirror (NALM)-based mode-locked thulium-doped fiber laser (TDFL) with a figure-eight configuration. Bright-dark pulse with 10 wavelengths was successfully obtained at the pump power of 3 W. The time interval between the bright and dark pulses was discovered not only increasing linearly with the pump power but also approximately equaling to the reciprocal of modulation frequency of radio frequency (RF) spectrum. Moreover, we also observed that the spectrum of split multi-wavelength bright-dark pulse can further present up to 13 wavelengths.     

利用非线性偏振旋转锁模技术产生0.7nJ,1.5ps光脉冲

为了研究锁模光纤激光器以增益平坦型掺铒光纤放大器作为增益介质对输出特性的影响,采用增益平坦型掺铒光纤放大器结合光纤偏振控制器、偏振相关光隔离器组成锁模光纤激光器,基于非线性偏振旋转锁模技术,实现稳定、自起振锁模运转,得到了中心波长1560nm、重复频率6.495MHz、单脉冲能量0.7nJ、脉宽1.5ps的超短光脉冲。同时实验观察到峰值波长为1557nm和1570nm的双峰值波长锁模脉冲的产生。结果表明,采用增益平坦型掺铒光纤放大器替代普通掺铒光纤组成锁模光纤激光器,可获得较高单脉冲能量的超短光脉冲,锁模脉冲的输出光谱可能出现双峰结构,从而可为超短脉冲光纤激光器设计及实用化提供参考。     

Feedback stabilized actively mode-locked Nd:phosphate glass laser

An electrooptic, actively mode-locked Nd: phosphate glass laser system is described employing a novel single-step feedback system to stabilize the pulse buildup time. Single output pulses of ∼100 ps duration with energies of up to 1 mJ could be reliably generated with a standard deviation in thesim3.2 mus pulse buildup time of ±40 ns allowing synchronization with pulses from laser systems at other wavelengths. Evidence of pulse broading due to self-phase modulation was observed together with wide tunability of the output wavelength from 1.054 to 1.068 μm.     

Diode-pumped passively mode-locked Nd3+-doped fluoridefiber laser emitting at 1.05 μm: novel results

The investigation of a novel seed source for Nd:glass or Nd:YLF regenerative amplifiers presented in an earlier work is extended. The new results demonstrate the versatility of the diode-pumped passively mode-locked Nd³⁺:ZBLAN fluoride fiber laser: pulses with durations from 9.2 ps to 320 fs, with center wavelengths in the range 1047-1060 nm, and with a maximum average output power of 4 mW could be generated. The amplitude noise was as low as 0.6% rms (150 Hz-100 kHz) and the longterm stability and reliability were impressive as well. Further, an evaluation of the capabilities of three different (analytical, semi-analytical, and numerical) models to predict the pulse durations is performed for laser setups used in our experiment     

Alternate and simultaneous generation of 1-GHz dual-wavelengthpulses from an electrically tunable harmonically mode-locked fiber laser

A new scheme of producing dual-wavelength mode-locked pulses from a fiber laser is proposed and experimentally demonstrated. In addition to the simultaneous generation of two selected wavelength components, the scheme also allows the alternate generation of mode-locked pulses at different wavelengths. The alternate switching of wavelengths is demonstrated at 1 GHz, and has been achieved over an electrical tuning range of 13.1 nm using the dispersion-tuning approach. A constant mode spacing of 7.1 nm is maintained during the tuning process     

All laser diode compression of 5 GHz picosecond pulses using cross-phase modulation in optical fibre

5 GHz pulses from a mode-locked semiconductor laser diode have been compressed from 10.5 to 4.6 ps by means of cross-phase modulation using a separate optically amplified mode-locked laser diode. By tuning the laser wavelengths symmetrically about the 1.55 mu m dispersion zero of an 11 km length of fibre, the effect of group velocity dispersion is minimised, ensuring that the fibre is used efficiently. The spectral broadening induced by the cross-phase modulation enables pulse compression in a dispersive fibre.<>     

波长可调谐光纤激光器

已成功研制了一台大功率宽调谐范围光纤激光器,利用主动锁模技术实现了光纤激光器的稳定脉冲输出。实验中调节偏振控制器到合适位置和调制器偏压为3．8V时,获得了平均输出功率2．160mW,重复率9．970754GHz,中心波长为1561．200nm的锁模脉冲输出,输出脉冲中心波长在1528．015-1571．330nm之间连续可调。     

10×30 GHz pulse train generation from semiconductor amplifierfiber ring laser

A multiwavelength, fiber ring laser source, is demonstrated. It generates 10 wavelength channels, simultaneously mode-locked and synchronized at 30 GHz, each producing 7-ps pulses. The mode-locking technique relies on the gain saturation of the semiconductor amplifier from an external optical pulse train to impose the simultaneous mode-locking of the 10 wavelengths