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.     

Tunable and switchable dual-wavelength passively mode-locked fiber ring laser with high-energy pulses at a sub-100 kHz repetition rate

We demonstrate a tunable and switchable dual-wavelength passively mode-locked fiber ring laser in the anomalous dispersion regime that generates high-energy pulses at a sub-100 kHz repetition rate. The nonlinear polarization rotation (NPR) technique is employed in this configuration to allow for passively mode-locked operation. By exploiting the intensity-dependent loss caused by NPR, the mode competition could be efficiently alleviated. Moreover, taking advantage of the intrinsic spectral filter induced by the intracavity birefringence, the dual-wavelength separations as well as the wavelength lasing locations could be flexibly tuned by properly rotating the polarization controller. With a repetition rate of 85.8 kHz, the laser delivers the single pulse energy of 198 nJ at a pump power of 250 mW. The combination of high per-pulse energy and flexible tunability in this fiber laser is useful for practical applications.     

Switchable single-longitudinal-mode dual-wavelength erbium-doped fiber ring laser incorporating a semiconductor optical amplifier

We propose and demonstrate a novel single-longitudinal-mode (SLM) dual-wavelength erbium-doped fiber ring laser incorporating a semiconductor optical amplifier. The SOA biased in its low-gain regime greatly reduces the gain competition of the two wavelengths. The stable SLM operation is guaranteed by a passive triple-ring cavity and a fiber Fabry-Perot filter. The dual-wavelength output with a 40 GHz wavelength spacing is switchable in the range of 1533-1565.4 nm.     

基于增益光纤长度优化的双波长运转掺铒光纤锁模激光器

构建了可自启动的双波长运转掺铒光纤锁模激光器.通过优化增益光纤长度,利用掺铒光纤在1530nm附近的再吸收效应调节激光器的增益谱,使激光器在1530nm和1560nm附近具有相同的增益强度.实验中采用31cm掺铒光纤作为增益光纤,以透射式半导体可饱和吸收体作为锁模器件,实现了自启动双波长锁模运转.激光器锁模输出重复频率为58.01MHz,信噪比为58.2dB,最高输出功率为4.8mW.锁模输出的光谱在1532.4nm和1552.3nm处具有两个强度接近的谱峰,谱峰间距约为20nm.该激光器无需手动调节即可实现双波长运转,更便于实际使用.     

Switchable multi-wavelength erbium-doped fiber lasers by using cascaded fiber Bragg gratings written in high birefringence fiber

A novel and simple Erbium-doped fiber laser by using cascaded fiber Bragg gratings (FBGs) written in high-birefringence fibers for switchable multi-wavelength operation is proposed. Due to two-peak reflection with orthogonal polarizations of the FBG, the polarization hole-burning effect in the cavity is greatly enhanced. Experimental results show that the stable dual- and three-wavelength lasing operation with very narrow wavelength separation (0.39 nm) can be generated at room temperature. The configuration is simple and flexible. Only by adjusting polarization controllers (PCs), the laser can be switched among the stable single-, dual- and three-wavelength lasing operations.     

超低频率全正色散半导体可饱和吸收镜被动锁模光纤激光器

 通过延长激光器环形腔腔长,利用高浓度掺杂的单模掺镱光纤,搭建了超低重复频率、全正色散结构的半导体可饱和吸收镜被动锁模光纤激光器。激光器的中心波长、重复频率、平均功率及单脉冲能量分别为1 064 nm,281.5 kHz,11 mW和39 nJ。为了稳定中心波长,实现自启动,激光器腔体内接入了一个带通滤波器。该激光器运行稳定,无调Q不稳定现象,极大减小了半导体可饱和吸收镜被损坏的机会。     

Actively mode-locked dual-wavelength fiber laser with close wavelength spacing using a fiber Bragg grating

A simple actively mode-locked fiber ring laser is proposed and successfully demonstrated to generate dual-wavelength picosecond pulses with close wavelength spacing using one Bragg grating in standard single-mode fiber. The proposed laser can be made to operate in stable dual-wavelength at room temperature, due to the birefringence characteristic of the FBG induced by transverse strain. Transverse strain loading on the FBG allows the wavelength spacing to be controlled. Generation of stable dual-wavelength pulses with a pulsewidth of 212–234 ps and a tunable wavelength separation from 0.2 to 0.44 nm at a pulse rate of 1.05 GHz was demonstrated.     

Double-ring cavity configuration of actively mode-locked multi-wavelength fiber laser with equally tunable wavelength spacing

A novel actively mode-locked multi-wavelength tunable fiber laser with equally increased or decreased wavelength spacing is presented. It is constructed using a double-ring cavity combined with an amplitude modulator and cascaded fiber Bragg gratings (FBGs). The cavity lengths for all FBGs are intrinsically identical due to the double-ring configuration, and simultaneous mode locking of multiple wavelengths is therefore achieved by applying only one mode-locking signal to the modulator. The FBGs are mounted on a organic plate with angles between adjacent gratings such that the forces applied to the FBGs have an equal force increment; thus, stretching or compressing the cascaded FBGs can achieve a wavelength tuning with equally increased or decreased wavelength spacing.This revised version was published online in March 2005. In the previous version, the published online date was missing     

Incorporate, switchable dual-wavelength fiber laser with Bragg gratings written in a polarization-maintaining erbium-doped fiber

A stable, incorporate and switchable dual-wavelength fiber laser with two fiber Bragg gratings written in a photosensitive and polarization-maintaining erbium-doped fiber directly, that is, without splices in the laser cavity, is proposed and demonstrated. Simultaneous dual-wavelength oscillation is achieved at room temperature with a wavelength spacing of 0.343 nm. The power fluctuation and wavelength shift of single-wavelength oscillations are measured to be less than 0.24 dB and 0.013 nm over 2 h. The wavelength switchability between single- and dual-wavelength oscillations is realized by altering the voltage upon the electrostrictive ceramic actuator.     

Modulation instability induced by cross-phase modulation in a dual-wavelength dispersion-managed soliton fiber ring laser

We report on the observation of the modulation instability induced by cross-phase modulation in a dual-wavelength operation dispersion-managed soliton fiber ring laser with net negative cavity dispersion. The passively mode-locked operation is achieved by using a nonlinear polarization rotation technique. A new type of dual-wavelength operation, where one is femtosecond pulse and the other is picosecond pulse operation, is obtained by properly rotating the polarization controllers. When the dual-wavelength pulses are simultaneously circulating in the laser ring cavity, a series of stable modulation sidebands appears in the picosecond pulse spectrum at longer wavelength with lower peak power due to modulation instability induced by cross-phase modulation between the two lasing wavelengths. Moreover, the intensities and wavelength shifts of the modulation sidebands can be tuned by varying the power of the femtosecond pulse or the lasing central wavelengths of the dual-wavelength pulses. The theoretical analysis of the modulation instability induced by cross-phase modulation in our fiber laser is also presented.     

全正色散多波长被动锁模耗散孤子掺镱光纤激光器

报道了一种带有周期性双折射光纤滤波器的全正色散多波长被动锁模耗散孤子掺镱光纤激光器. 通过数值模拟发现加入滤波器后激光器能输出多波长耗散孤子脉冲, 调节滤波器带宽大小可以得到不同波长个数和波长间隔的多波长锁模耗散孤子脉冲. 在激光器产生的四波长和五波长耗散孤子脉冲中观察到了耗散孤子分子, 并且通过调节滤波器参数和饱和功率可以改变多波长脉冲中耗散孤子分子的个数和波长. 这是在被动锁模光纤激光器中首次实现包含有耗散孤子分子的多波长脉冲. 另外还在实验上实现了全正色散双波长被动锁模耗散孤子的产生. 关键词： 全正色散 耗散孤子 多波长脉冲 孤子分子     

Stable dual-wavelength erbium-doped fiber ring laser with switchable spacing employing controllable channel loss

A stable dual-wavelength erbium-doped fiber ring laser with switchable spacing is proposed and experimentally demonstrated. An arrayed waveguide grating (AWG) incorporating two fiber optic switches (OS) is used to as the wavelength selector. The ring cavity is divided into two cavities by a 30:70 optical coupler. Equalized dual-wavelength outputs are achieved by controlling the variable optical attenuator (VOA) inserted in the lower loss cavity. The wavelength spacing can be tuned from 0.80 to 12.05 nm. The fiber laser has good optical quality with maximum power fluctuation of 1.5 dB and side mode suppression ratios (SMSRs) higher than 71 dB.     

Switchable dual-wavelength polarization-maintaining erbium-doped fiber laser using an optical circulator as the all-reflecting mirror

A simple and effective switchable dual-wavelength polarization-maintaining erbium-doped fiber laser is proposed and demonstrated. Only using a uniform fiber Bragg grating written directly in a segment of the photosensitive and polarization-maintaining erbium-doped fiber as the wavelength selector and an optical circulator as the all-reflecting mirror, a stable simultaneous dual-wavelength oscillation is achieved with a wavelength spacing of 0.364 nm experimentally by exploiting the polarization hole burning effect at room temperature. The output can be switched between single- and dual-wavelength by adjusting the polarization controller. The 3-dB bandwidth and the side mode suppression ratio of the laser’s outputs are measured to be less than 0.01 nm and more than 50 dB. The power fluctuation and wavelength drift are measured to be less than 0.50 dB and 0.020 nm over an hour.     

Highly efficient dual-wavelength ytterbium-doped fiber linear cavity laser based on cascaded fiber Bragg gratings

A highly efficient dual-wavelength ytterbium-doped fiber linear cavity laser is experimentally demonstrated. Two cascaded fiber Bragg gratings are used as the wavelength selection component. Stable dualwavelength operation and wavelength-switching modes can be realized by appropriately adjusting the polarization state of the intra-cavity light and the reflectivity of the laser cavity. For dual-wavelength operation, the power difference between the two wavelength lasers (1029.7 and 1040.4 nm) can be less than 0.6 dB and the signal-to-amplified spontaneous emission (ASE) ratio is more than 52 dB. The slope efficiency of the laser is as high as 63.9%.     

Tunable and Switchable Narrow Bandwidth Semiconductor-Saturable Absorber Mirror Mode-Locked Yb-Doped Fiber Laser Delivering Different Pulse Widths

The wavelength-tunable and switchable narrow bandwidth mode-locking operation is demonstrated in an all fiber laser based on semiconductor-saturable absorber mirror(SESAM).Two narrow-band fiber Bragg gratings centered at 1029.9 nm and 1032 nm respectively with a polarization controller inserted between them are used to realize the wavelength switchable between 1029.9nm and 1032 nm.The laser delivers different pulse widths of 7.5ps for 1030 nm and 20 ps for 1032 nm.The maximum output power for both could reach ~6.5mW at single pulse operation.The output wavelength could be tuned to about 0.9nm intervals ranging from 1030.2nm to 1031.1 nm and from 1032.15 nm to 1033.7nm with the temperature change of the fiber Bragg grating,respectively.     

Intrinsic dual-wavelength operation of a passively mode-locked fiber ring laser

We report on the dual-wavelength operation in an erbium-doped fiber ring laser mode-locked through nonlinear polarization rotation technique. In addition to dual-wavelength continuous wave operation, alternative mode-locking at the dual wavelengths was realized experimentally. By analyzing the transmissivity of the laser cavity, we find the dual-wavelength operation is an intrinsic feature of the laser associating with the dispersive cavity loss. Numerical simulations confirm the experimental and theoretical results and further demonstrate that the location of the dual wavelengths and the separation between them closely depend on the cavity birefringence and the profile of the gain medium.     

Tunable microwave photonic notch filter using a dual-wavelength fiber laser with phase modulation

A novel tunable microwave photonic notch filter using a phase-modulated dual-wavelength fiber laser is presented. A stable dual-wavelength erbium-doped fiber laser with a linear cavity is formed by a polarization-maintaining uniform fiber Bragg grating (PM-FBG) and a polarization maintaining linearly chirped fiber Bragg grating (PM-LCFBG), both of which were fabricated on a high-birefringence (Hi-Bi) fiber. It is found that a stable room-temperature dual-wavelength operation can be achieved due to the presence of two reflection peaks arising from the orthogonal states of polarization (SOP) of the PM-FBG. Experimental results show stable dual-wavelength lasing operation with a wavelength separation of ∼0.36 nm and a large optical signal-to-noise ratio (OSNR) of over 40 dB under room temperature. The dual-wavelength fiber laser is combined with a phase modulator and a segment of single-mode fiber (SMF) as a dispersive device to form a tunable microwave photonic notch filter. By stretching the PM-FBG to tune the wavelength separation of the dual-wavelength fiber laser, a tunable microwave photonic notch filter with various free spectral ranges (FSRs) and a rejection ratio greater than 35 dB was developed.     

Stable single- and dual-wavelength fiber laser mode locked and spectrum shaped by a Fabry-Perot saturable absorber

We show that the spectral response of a Fabry-Perot semiconductor saturable absorber depends on laser beam focusing. We used this effect to achieve stable passive mode-locked operation in a simple and environmentally stable fiber laser by introducing spectral filtering and forcing near-resonant operation. By reducing the free spectral range and increasing the nonlinear response of the Fabry-Perot saturable absorber, we obtained dual-wavelength mode-locked operation.     

A novel dual-wavelength fiber Bragg grating and its application in fiber ring laser

A novel method for fabricating dual-wavelength fiber Bragg gratings (FBGs) by using one phase mask is developed. The method is based on a double-exposure technique. Our technique lends itself to writing gratings with controllable reflectivity and separation of two Bragg wavelengths. A grating with two equal transmission peaks of 20.25 dB is obtained by this method and the separation of the two Bragg wavelengths is about 0.8 nm. With the grating, we demonstrate a dual-wavelength erbium-doped fiber ring laser whose interval of the two peaks is 0.8 nm. The laser's peak powers can get 3.1 mW above and have a good stability.     

Switchable single- and dual-wavelength erbium-doped fiber laser assisted by four-wave mixing with wide and continuous tunability

A widely tunable and stable erbium-doped fiber laser based on four-wave mixing effect in a highly nonlinear fiber is proposed and experimentally demonstrated. By adjusting reflected power from a dual-selective element, the ring laser is switchable between single- and dual-wavelength operations. The tuning range of the single laser is 22.78 nm, from 1,542.07 to 1,564.85 nm, while the wavelength spacing of the dual-wavelength can be continuously tuned from 0.52 to 22.78 nm. The laser is stable with output peak power fluctuation of <1 dB in 30-min interval.