1560nm激光经PPLN和PPKTP晶体准相位匹配倍频研究

将1560nm光栅反馈复合腔半导体激光器产生的连续激光注入掺铒光纤放大器,放大至约5 W,分别采用周期极化铌酸锂(PPLN)和周期极化磷酸氧钛钾(PPKTP)晶体单次穿过进行准相位匹配倍频,对应获得约336mW和210mW的780nm激光输出,倍频效率约为7%和4.4%。通过监视倍频光纵模,显示其具有良好的单频输出特性。此外,还扫描测得了Rb原子D2线的吸收光谱,表明780nm激光的频率调谐范围大于10GHz。采用无调制偏振光谱技术将1560nm半导体激光器频率锁定至87 Rb 5S1/2(Fg=2)-5P3/2(Fe=3)超精细跃迁线上。相对于自由运转450s内1560nm激光频率起伏约4MHz,锁定后可将残余频率起伏压低至1.5MHz左右。     

不同波长的激光器通过法布里-珀罗腔相对于铯原子谱线的锁定

采用共焦法布里珀罗腔(CFP)作为桥梁,可以实现不在原子、分子跃迁线附近的单频激光器相对于原子、分子跃迁线的锁定,从而可以有效地抑制激光频率的漂移。在实验中通过射频频率调制光谱技术结合饱和吸收光谱(SAS)将自制852nm光栅外腔反馈半导体激光器锁定到铯6S1/2Fg=4-6P3/2Fe=4、5交叉线上,通过Pound-Drever-Hall(PDH)射频边带技术将作为桥梁的共焦法布里珀罗腔锁定在852nm激光频率上。再通过PDH方法将830nm和908nm两台远离铯原子D2线的外腔半导体激光器同时锁定在作为桥梁的共焦法布里珀罗腔上,实现了830nm和908nm两台激光器相对于铯原子跃迁线的锁定。由锁定后的误差信号估算,20s内852nm激光器相对于铯原子Fg=4-Fe=4、5交叉线的频率起伏小于±540kHz,830nm、908nm激光器相对于共焦法布里珀罗腔的频率起伏分别小于±340kHz和±60kHz,共焦法布里珀罗腔相对于852nm激光的频率起伏小于±550kHz。     

基于噪声免疫腔增强光外差分子光谱技术实现光纤激光器到1530.58 nmNH_3亚多普勒饱和光谱的频率锁定

噪声免疫腔增强光外差分子光谱技术(NICE-OHMS)由于结合了频率调制光谱与腔增强光谱两种技术,不仅可以将激光耦合到高精细度谐振腔大幅提高腔内功率,还可以实现低气压样品气体的高灵敏测量,因此基于该技术可以实现分子吸收线的饱和,获得亚多普勒光谱,从而能作为激光频率锁定的参考.本文基于光纤激光器的NICE-OHMS技术,将光纤激光器频率锁定到NH3的亚多普勒吸收线上.首先分析了基于Pound-Drever-Hall和DeVoe-Brewer技术实现激光到腔模和调制频率到腔自由光谱区频率锁定的性能,之后在腔内气压为70 mTorr条件下,测量了半高全宽为2.05 MHz的NH3亚多普勒信号,最后将1.53μm的光纤激光器频率锁定到该亚多普勒吸收线上,相对频率偏差为16.3 kHz,阿伦方差结果显示,136 s积分时间下频率稳定度达到1.6×10~(-12).     

声光偏频亚多普勒光谱无调制激光频率锁定

将激光器锁定到合适的参考频率标准上 ,可以有效地改善激光器的频率稳定性。采用两个声光调制器(AOM) ,使铯原子D2 线饱和吸收光谱分别发生Ω±Δ绝对频移 ;通过改变射频压控振荡器 (RFVCO)的Vf 端口直流电压调节相对频移间隔Δ ,当相对频率间隔选择合适时两信号相减得到了类色散型鉴频曲线。实验中实现了85 2nm光栅外腔半导体激光器相对于铯原子D2 线6S1/2 F =4 6P3 /2 F′ =5超精细跃迁线 (中心频率ν0 )的无调制偏频锁定 (锁定后中心频率ν0 +Ω ,偏频量为Ω)。由闭环锁定后的误差信号估计 ,5 0s内典型的频率起伏小于± 2 70kHz ,较相同时间段内激光器自由运转时的频率起伏 14MHz有显著的改善。该方法可避免对激光器直接进行频率调制的常规饱和吸收锁频方案所引入的额外频率噪声和强度噪声。     

锶原子光钟中repumping光频率锁定系统的研制

锶原子光钟里两束repumping光的频率对应锶原子三重态系跃迁(5s5p)3P0-(5s6s)3S1和(5s5p)3P2-(5s6s)3S1,由于其跃迁基态处于亚稳态,所以较难利用原子的跃迁线作为参考对这两台激光器进行锁频.本文介绍一种基于腔传递的数字伺服系统实现这两台半导体激光器任意频率的同时锁定.通过一台F-P腔将He-Ne激光器的频率高稳定性同时传递到两台受控激光器上.LabVIEW程序自动搜索激光透射峰信号从而得到误差信号,由比例积分算法得出控制电压,并反馈回激光器.可视化界面易于操作和观察,可直接完成对激光器的锁定,并自动记录实验结果.该方法使用方便,锁定后激光器频率波动为±4 MHz左右.该系统易扩展,可实现多台激光器的同时锁定.将锁定后的repumping光加入蓝MOT后,磁光阱内俘获的原子荧光强度增大了12倍,寿命提高了13倍,对于锶原子光钟一级冷却的研制有重要的应用价值.     

半整块外腔谐振倍频稳频MgO：LiNbO3激光器

报道了,用高功率LD泵浦的全固化单频稳频Nd:YVO4激光器作为泵浦源的外腔谐振倍频绿光激光器,倍频腔采用半整块腔型,倍频晶体为MgO:LiNbO3,当倍频腔前的基频光功率为1W时,得到最高绿光输出为500mW,倍频转换效率为50％,在锁定情况下,倍频腔的功率波动小于2％,频率稳定性优于500KHz。     

激光器频率稳定性的分析优化

在相干光通信中,激光器的频率稳定性是相当重要的,压缩光源的频率噪声不仅可以降低通信的误码率,而且能够增大系统的安全传输距离,以此提高通信质量。而且在其它领域低频率噪声光源也应用广泛。将正弦调制信号加载到激光器电流调制端口进行波长调制,以乙炔气体的吸收线作为频率参考将激光器频率锁定在乙炔吸收线上,利用单光子波长调制技术实现对DFB激光器的频率锁定。     

激光二极管相对于铯饱和吸收D2线的无调制扰动三次谐波锁频

将频率调制加在声光调制器上 ,用三次谐波探测法获得了铯原子D2 线的三阶微分饱和光谱。采用这种激光器无调制扰动方案结合三次谐波锁频技术 ,实现了 85 2nm的分布布拉格反射器半导体激光器相对于 6S1/2 F =4- 6P3 /2 F′ =5超精细跃线的频率锁定。由锁定后的频率误差信号估算 ,10s内激光频率起伏小于± 35 0kHz ,相对频率稳定度约 1× 10 -9。这种无调制扰动方案可以消除一般的饱和吸收稳频方法中由于直接对激光器进行频率调制而带来的额外频率噪声 ;三次谐波锁频技术的应用 ,还可有效地降低铯原子饱和吸收谱中剩余多普勒背景的影响     

基于Rydberg原子EIT光谱的激光频率锁定

本文利用Rydberg阶梯型三能级系统的电磁诱导透明光谱实现了509nm倍频激光器的无调制频率锁定。我们在实验中使用852nm激光和509nm激光在铯原子蒸汽池中构成阶梯型三能级体系,852nm激光器的频率锁定在铯原子6S1/2→6 P3/2共振跃迁线上,509nm激光在铯原子激发态6 P3/2→62 D5/2Rydberg态的跃迁频率附近扫描获得了Rydberg态的电磁诱导透明光谱。利用852nm半导体激光器的频率调制作为参考信号,对探测的电磁诱导透明光谱信号进行解调得到误差信号,实现了509nm激光器的频率锁定。通过分析误差信号的频谱,对伺服电路的低频和高频反馈参数进行优化,获得的最佳锁定线宽约为533kHz,最小阿伦方差达到1.5×10-11。     

光学锁相环的实现及其在铯原子四波混频过程中的应用

我们利用自制的光学锁相环实现了一台外腔半导体激光器和一台钛宝石激光器的相对频率和相对相位锁定,锁定后两束光的拍频线宽约为1 Hz。同时,该光学锁相环能实现两台激光器从10 MHz至10GHz任意频率差的锁定,通过简单升级射频元件可以实现最高20 GHz频率差的锁定,可应用于激光冷却与俘获原子、光与原子相互作用等研究领域。我们实验证明将该锁相环应用于铯原子蒸汽中的四波混频过程,产生的孪生光束最大强度差压缩由3.8dB提高至6.0dB。     

LD侧面抽运Nd∶YAG多波长激光器

利用单根Nd∶YAG晶体棒,实现1 064 nm和1 319 nm双波长基频光振荡及其倍频光532 nm、660 nm激光的输出.采用LD侧面抽运单根Nd∶YAG晶体棒实现1 064 nm和1 319 nm基频光振荡,在此基础上使用非线性频率变换技术获得532 nm和660 nm倍频光的输出.结果表明:1 064 nm和1 319 nm基频激光同时输出时功率分别为30.5 W和8.78 W,单独输出时功率分别为35.6 W和11.2 W|在声光调Q频率分别为10.5 kHz和20.5 kHz时,获得了功率分别为5.34 W和1.353 W的532 nm激光和660 nm激光两路同时运转输出、功率分别为6.72 W和1.902 W各路单独输出,两种情况下倍频转换效率均为17.5%和15.4%,不稳定度小于2%.     

高效腔外频率变换紫外激光器

 为了得到高效的腔外频率变换355 nm紫外激光输出,提出了一种利用３块LBO作为非线性频率变换晶体的新方案。采用LD端面泵浦Nd：YAG声光Q开关激光器作为基波源,当入射泵浦功率为25 W、调制频率12 kHz时,获得了6.2 W的1 064 nm激光输出,经过非线性频率变换后,获得了2.7 W的紫外355 nm激光输出,光-光转换率43.4%。     

555 nm laser sources based on intracavity frequency doubling of Nd:YGG laser

We report for the first time a yellow-green laser at 555 nm generation by intracavity frequency doubling of a continuous wave (CW) laser operation of a 1110 nm Nd-doped yttrium gallium garnet (Nd:YGG) laser under in-band diode pumping at 808 nm. An LBO crystal, cut for critical type I phase matching is used for second harmonic generation of the laser. At an incident pump power of 18.5 W, as high as 2.31 W of CW output power at 555 nm is achieved. The optical-to-optical conversion efficiency is up to 12.4%, and the fluctuation of the yellow-green output power was better than 2.8% in the given 4 h.     

All solid-state CW Nd:LuVO<Subscript>4</Subscript>-LBO yellow-green laser under direct 888 nm pumping

We report a yellow-green laser at 544.5 nm generation by intracavity frequency doubling of a continuous wave (CW) laser operation of a 1089 nm Nd:LuVO₄ laser under in-band diode pumping at 888 nm. An LBO crystal, cut for critical type I phase matching is used for second harmonic generation of the laser. At an incident pump power of 17.9 W, as high as 3.81 W of CW output power at 544.5 nm is achieved. The optical-to-optical conversion efficiency is up to 21.3%, and the fluctuation of the yellow-green output power was better than 3.7% in the given 4 h.     

高效全固化紫外四倍频激光器的研究

用半导体激光器抽运的调Q YLF倍频激光器抽运掺钛蓝宝石激光器，用LBO晶体在腔内产生二次谐波，再聚焦到BBO晶体上产生四次谐波深紫外激光。为了提高谐波转换效率，在腔内分别插入了单片、组合双折射滤光片和聚焦透镜，在平均功率为3.6W，波长为527nm的抽运光下得到410mW，417nm的蓝光。用长焦距的透镜聚焦二次谐波，得到34mW，208nm的紫外脉冲激光。从实验上详细研究了基频光的线宽对二次谐波效率的影响，二次谐波的线宽对四次谐波效率的影响、基频光的波长对四次谐波产生效率的影响。全面地分析了单片和组合大拆射滤光片及抽运功率对钛蓝宝石激光器基频光的脉宽、线宽等参量的影响。     

A Micro Blue-violet Laser by Frequency Doubling of Semiconductor Laser

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　　Ｔｈｅｂｌｕｅ ｖｉｏｌｅｔｌａｓｅｒｉｓｕｓｅｄｉｎｍａｎｙｆｉｅｌｄｓｓｕｃｈａｓｏｐｔｉｃａｌｉｎｆｏｒｍａｔｉｏｎｓｔｏｒａｇｅ,ｏｐｔｉｃａｌｃｏｍｍｕｎｉｃａｔｉｏｎ,ｄｉｓｐｌａｙ,ｅｔｃ..Ｉｔｃａｎｂｅｒｅａｌｉｚｅｄｆｒｏｍｆｒｅｑｕｅｎｃｙｄｏｕｂｌｉｎｇｏｆａｓｅｍｉｃｏｎｄｕｃｔｏｒｌａｓｅｒａｔｒｏｏｍｔｅｍｐｅｒａｔｕｒｅ.Ｔｈｉｓｌｉｇｈｔｓｏｕｒｃｅｈａｓｔｈｅａｄｖａｎｔａｇｅｓｏｆａｌｌ ｓｏｌｉｄ ｓｔａｔｅ ,ｃｏｍｐａｃｔｎｅｓｓ,…     

Continuous wave Nd:YAG-BiBO blue laser under direct 869 nm pumping

We report a blue laser at 473 nm generation by intracavity frequency doubling of a continuous wave (CW) laser operation of a 946 nm Nd:YAG laser under in-band diode pumping at 869 nm. An BiBO crystal, cut for critical type I phase matching at room temperature is used for second harmonic generation of the laser. At an incident pump power of 8.6 W, as high as 721 mW of CW output power at 473 nm is achieved. The optical-to-optical conversion efficiency is up to 8.4%, and the fluctuation of the blue output power was better than 3.5% in the given 30 min.     

Generation of 7.8 W at 355 nm from an efficient and compact intracavity frequency-tripled Nd:YAG laser

A high power, quasi-continuous wave ultraviolet laser at 355 nm was obtained by intracavity frequency tripling of a diode side-pumped acousto-optic (AO) Q-switched Nd:YAG laser. Type II critical phase-matched KTP and LBO crystals were used for the second harmonic generation and the third harmonic generation, respectively. Under the pump power of 180 W, 7.8 W average output power at 355 nm was obtained at 8 kHz with the pulse width of 50 ns, corresponding to the pump-to-ultraviolet conversion efficiency of 4.3%. The peak power and single pulse energies were estimated to be 18.8 kW and 938 μJ. Its far-field divergence was measured to be about 3.8 mrad. The instability of the 355 nm laser was less than 1% at an output power of 6.3 W for 2 h operation.     

All-solid-state low noise Yb:YAG/LBO green laser at 515 nm

We report the efficient compact green laser at 515 nm generation by intracavity frequency doubling of a continuous wave (CW) laser operation of a diode-pumped Yb:YAG laser on the transition at 1030 nm. An LBO crystal, cut for critical type I phase matching at room temperature is used for second harmonic generation (SHG) of the laser. With the incident pump power of 10 W, 270 mW of CW output power at 515 nm is achieved with 15-mm-long LBO. The optical-to-optical conversion efficiency is 2.7%, and the power stability in 8 h is better than 2.36% with low noise.     

Diode-pumped Nd:LGS/LBO laser at 452 nm

We report a blue laser at 452 nm generation by intracavity frequency doubling of a continuous wave (cw) laser operation of a 904 nm Nd:LGS laser under 808 nm diode pumping. A LiB₃O₅ (LBO) crystal, cut for critical type I phase matching at room temperature is used for second harmonic generation (SHG) of the laser. At an incident pump power of 17.8 W, as high as 1.14 W of cw output power at 452 nm is achieved. The optical-to-optical conversion efficiency is up to 6.4%, and the fluctuation of the blue output power was better than 4.1% in the given 30 min.