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1.
研究了在各向异性外腔下微片Nd:YAG激光器调频回馈特性.作为对比,首先给出了在各向同性外腔下调频回馈结果,激光器输出功率的半波条纹数正比于外、内腔长度之比.在回馈外腔中内置一个四分之一波片,激光偏振态发生规律性跳变,每个纵模带宽内的偏振跳变次数正比于外、内腔长之比,相同外腔长下,回馈条纹再次倍频.进行了基于法布里-珀罗腔等效模型的理论分析,结果和实验相符合.此现象在精密测量领域有潜在应用.
关键词:
光回馈
调频回馈
各向异性外腔
半波条纹数 相似文献
2.
3.
The self-mixing interference effects are investigated in birefringence dual-frequency Nd:YAG lasers at different optical feedback
levels. For weak feedback level, both of the intensities of the two modes are sinusoidally modulated by external cavity length
with a feedback period of half laser wavelength. While these two modes can only coexist in a part of feedback period at moderate
feedback level, i.e., one mode reaches its maximum intensity, the other one extinguishes. At high feedback level, complete
polarization switching (one mode oscillating, the other one extinguishing) between two polarized modes is observed, and every
switching corresponds to quarter-wavelength variation of external cavity length. Furthermore, two feedback schemes, i.e.,
isotropic optical feedback (IOF) and polarized optical feedback (POF) are taken into account. The theoretical analysis based
on a model of two-mode-coupled laser is presented, which is in good agreement with experimental results. Our results can advance
the research of self-mixing interferometer of orthogonally polarized dual-frequency lasers. 相似文献
4.
The optical feedback characteristics in a Zeeman-birefringence HeNe laser have been studied systematically when the external cavity varies in a large range. The intensity variations of the two orthogonally polarized lights are observed during the laser cavity tuning in the dual frequency laser. When the external cavity length is an integral multiple of the laser cavity length, either polarized light's intensity modulation depth varies not obviously when the laser works in dual modes conditions or single mode condition. But when the external cavity length is far away from an integral multiple of the laser cavity length and the laser works in different dual modes conditions, polarized light's intensity modulation depth varies obviously. This characteristic can guide us to tune the laser to work in single mode condition to improve the sensitivity of the optical system when the system is used for a large displacement measurement. It can also be used for measuring the position of the target mirror. The theoretical analysis is in good agreement with experimental results. 相似文献
5.
研究了Nd:YAG激光器中光回馈引起的多模跳变现象.光回馈调制了激光器不同纵模的阈值增益,阈值增益最低的纵模获得振荡.在外腔调谐过程中,当振荡模式的阈值增益高于相邻模式的阈值增益时产生模跳变,光强调制曲线出现相应的波动.各跳变纵模在增益曲线上的位置不同,导致模跳变点位置不同,相应的光强调制曲线也不同.越靠近中心频率的纵模,其光强信号峰值越大,该纵模持续振荡时间也就越长.当两跳变纵模关于中心频率对称时,其光强信号峰值相等,纵模持续振荡时间也相等.
关键词:
自混合干涉
模跳变
光回馈
阈值增益 相似文献
6.
We present the effects of single high-order round-trip feedback in orthogonally polarized dual frequency laser. The high quality intensity fringes of two orthogonally polarized lights are obtained, which are cosine-like. The fringe frequency of a single high-order round-trip feedback is five times that of the conventional optical feedback. Even higher frequencies are possible with this setup. Particularly, there is a phase difference between two orthogonal polarized lights in single high-order round-trip feedback and the phase difference is determined by the feedback order, the length of the external cavity, and the frequency difference of the two orthogonal polarized lights. A theoretical analysis based on a compound cavity model of a dual frequency laser agrees well with the experimental results. These results provide a potential application in precision measurement with both directional discrimination and high optical resolution. 相似文献
7.
微片激光器由于自身的内应力会输出频率分裂的正交偏振的两个模式.研究了回馈对微片激光器频差的影响.研究发现:在回馈的作用下微片激光器的频差大小呈现出以初始频差为中心的类正弦的频差调制,周期为λ/2;频差调制曲线的幅度与回馈水平成正比,但是当回馈水平过强时会出现偏振态跳变,从而使频差消失;在一定的回馈外腔范围内,频差调制曲线的幅度与初始频差亦成正比.并利用复合腔模型和激光器的自洽理论进行了理论分析和模拟,所得结果与实验结果相符.此调制现象在精密测量领域有潜在应用. 相似文献
8.
玻璃材料的内应力关系及所在系统的稳定性、安全性和可靠性,是精密加工领域的重要问题.基于双折射外腔激光回馈效应的应力测量技术以其先进新颖的测量原理受到普遍关注.传统理论普遍认为双折射回馈系统中激光器的输出相位仅由外腔相位延迟决定,而将测量误差归因于外腔镜的非线性运动.本文结合正交偏振激光原理和三镜腔等效模型,测量了激光器的内腔双折射引起的频差大小,进行了频率调谐回馈实验,并根据结论计算了内腔频差对外腔相位延迟测量结果的影响,发现激光器的输出相位由外腔相位延迟、内腔频差、外腔长度共同决定.本文总结了内腔和外腔各向异性共同作用下激光器正交偏振态的相位特性,补充了激光回馈的物理内容,对于应力-双折射、位移、距离等重要参量的精确测量,都具有重要指导意义. 相似文献
9.
激光二极管自混合干涉的计算分析和实验观察 总被引:4,自引:1,他引:3
实验上观察到自混合干涉信号的幅度仅仅为静态光强的百分之几.反馈光会引起激光二极管阈值电流减小,静态输出光强变化几倍,使激光二极管工作在实际的阈值电流之上.按三镜法布里-珀罗腔结构模型计算激光二极管的出射光强,由干涉函数主极大条件得出光频与反馈光的关系.计算出的自混合干涉信号的波形,以及自混合干涉信号的幅度与静态光强的比值均同实验测量结果一致.在τrC/τ1=22.8的情况下,复合谐振腔可同时有15个谐振模式,这些模随外腔长度的变化小于2.6×10-2cm-1,远小于法布里-珀罗谐振腔谐振模的线宽3.1cm-1,光频在内腔谐振模的线宽以内变化. 相似文献
10.
Intensity modulation in single-mode microchip Nd:YAG lasers with asymmetric external cavity
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Intensity modulation induced by the asymmetric external cavity in
single-mode microchip Nd:YAG lasers is presented. Two kinds of experimental
results are discussed based on multiple feedback effects. In one case, the
intensity modulation curve is a normal sine wave, whose fringe frequency is
four times higher than that of a conventional optical feedback system,
caused by multiple feedback effects. In the other case, the intensity modulation
curve is the overlapping of the above quadruple-frequency signal and
conventional optical feedback signal, which is determined by the additional
phase difference induced by the asymmetric external cavity. The theoretical
analyses are in good agreement with the experimental results. The
quadruple-frequency modulation of the laser output intensity can greatly
increase the resolution of displacement measurement of an optical feedback
system. 相似文献
11.
针对光纤激光器自混合干涉传感应用,研究了光纤激光器自混合干涉特性,运用四镜法布里-珀罗腔模型对掺铒线形腔光纤激光器自混合干涉效应进行了理论分析,对不同反馈水平下的自混合干涉信号进行了数值模拟,获得了光反馈条件下光纤激光器输出特性.外腔长度的改变会调制激光器的输出强度,外腔长度变化半个波长,对应一个干涉条纹,弱反馈条件下,由反馈引起的激光器的频率变化可以忽略.设计了基于光纤激光器的自混合干涉实验,实验结果和理论分析相符合.此研究结果为进一步开展光纤激光器的自混合干涉传感应用研究奠定了理论与实验基础. 相似文献
12.
Polarization switching in a quasi-isotropic microchip Nd:YAG laser induced by optical feedback
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This paper demonstrates the influence of external optical
feedback on the polarization state of longitudinal modes in
quasi-isotropic microchip Nd:YAG lasers. Under optical feedback, the
polarization state of longitudinal modes in quasi-isotropic lasers
relies strongly on the intracavity anisotropy loss and mode
competition. When the intracavity anisotropy loss is small, external
optical feedback can cause polarization switching and strong mode
competition between two orthogonal linearly polarized eigenstates of
one laser longitudinal mode, which leads to the distortion of laser
intensity modulation waveform. The polarization switching is
independent of the initial external cavity length. By increasing the
intracavity anisotropy loss, one polarization eigenstate can be
suppressed and the laser works in single-polarization state. A
theoretical analysis based on the compound cavity model is
presented, which is in good agreement with the experimental results.
The results offer guidance to the development of laser feedback
interferometers. 相似文献
13.
Optical feedback characteristics in a helium neon laser with a birefringent internal cavity
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The output characteristics of optical feedback in a helium neon laser with a birefringent internal cavity are studied systematically in five different regions of the gain curve for the two orthogonally polarized modes. When the laser operates in the two end regions of the laser gain curve, one of the two orthogonally polarized modes will be a leading one in optical feedback. Strong mode competition can be observed. However, when the laser operates in the middle region of the laser gain curve, the two modes can oscillate equally with optical feedback. Besides the intensity of the two polarized lights, the total light intensity is also studied at the same time. M-shaped optical feedback curves are found. Particularly, when the average intensities of the two lights are comparable, the intensity modulation curve of the total light is doubled, which can be used to improve the resolution of an optical feedback system.[第一段] 相似文献
14.
The mode hopping phenomenon induced by optical feedback in single-mode microchip Nd:YAG lasers is presented. With optical feedback, mode hopping strongly depends on two factors: the ratio of external cavity length to intra-cavity length, and initial gains of the two hopping modes, When external cavity length equals an integral multiple of intracavity length, there is almost no mode hopping. However, if the external cavity length does not equal an integral multiple of intra-cavity length, mode hopping occurs. The ratio of external cavity length to intra-cavity length determines the position of two-mode hopping, The initial gains of the two hopping modes determine the corresponding peak values and oscillating periods of them in the intensity modulation curves. 相似文献
15.
Strong optical feedback in a birefringent dual frequency He--Ne laser with a
high reflectivity feedback mirror has been investigated for the first time.
The output characteristics of two orthogonally polarized modes are
demonstrated in two different optical feedback cases: one is for both modes
being fed back and the other is for only one of the modes being fed back.
Strong mode competition can be observed between the two modes with strong
optical feedback. And when one mode's intensity is near its maximum, the
other mode is nearly extinguished. When both modes are fed back into the
laser cavity, the mode competition is stronger than when only one mode is
fed back. The difference in initial intensity between the two orthogonally
polarized modes plays an important role in the mode competition, which has
been experimentally and theoretically demonstrated. 相似文献
16.
Anisotropic optical feedback of single frequency intra-cavity He--Ne laser 总被引:1,自引:0,他引:1
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This paper presents the anisotropic optical feedback of a single
frequency intra-cavity He--Ne laser. A novel phenomenon was
discovered that the laser output an elliptical polarized frequency
instead of the initial linear polarized one. Two intensities with a
phase difference were detected, both of which were modulated in the
form of cosine wave and a fringe shift corresponds to a λ/2
movement of the feedback mirror. The phase difference can be
continuously modulated by the wave plate in the external cavity.
Frequency stabilization was used to stabilize the laser frequency so
as to enlarge the measuring range and improve the measurement
precision. This anisotropic optical feedback system offers a
potential displacement measurement technology with the function of
subdivision of λ/2 and in-time direction judgment.
The three-mirror Fabry--Perot cavity model is used to present the
experimental results. Given the lack of need of lasing adjustment,
this full intra-cavity laser can significantly improve the
simplicity and stability of the optical feedback system. 相似文献
17.
We present a systematic study of external optical feedback effects on the output characteristics of the two orthogonally polarized modes in a frequency locking dual frequency laser. Accompanied by the change of the external cavity length, the length of the resonance cavity is changed very slowly to set the oscillating modes sweeping across the laser gain curve. Comprehensive results are obtained and a strong mode competition is observed. Particularly, when the laser runs in the middle region of the gain curve, which mode can oscillate is determined by the movement direction of the external feedback mirror. Based on the phenomenon, a displacement sensor with directional discrimination is proposed and its capability is also discussed. 相似文献
18.
The stability enhancement of laser output power for the change of external cavity position in semiconductor lasers with optical feedback is observed by experiment. The relaxation oscillation frequency which plays an important role in the dynamics of the nonlinear system is also investigated as a function of the external cavity length. The period of the stability enhancement along the position of the external cavity is exactly coincident with the length corresponding to the relaxation oscillation frequency of the solitary laser. The experimental results are compared with theoretical and excellent coincidence between the two is found. 相似文献
19.
J. Dellunde C. R. Mirasso M. C. Torrent J. M. Sancho E. Hernández-García 《Optical and Quantum Electronics》1995,27(8):755-760
The transient dynamics of a single-mode semiconductor laser subjected to both weak optical feedback and light injection is studied. Even at detuning values for which injection locking is not effective, turn-on jitter and frequency jitter can still be strongly reduced by adjusting either the length of the external cavity or the detuning. 相似文献
20.
Intensity modulation characters of orthogonally polarized HeNe lasers with different optical feedback level
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This paper demonstrates the intensity modulation characters of orthogonally polarized HeNe lasers with different optical feedback level generated by the variable reflectivity of external reflector. The modulation depths of the orthogonally polarized frequencies are increased when the optical feedback level becomes strong. It also observes that the modulation amplitudes are different for different external cavity length. Based on the vectorial extension of Lamb's semi-classical theory, it finds that the calculations are consistent with the experimental results. 相似文献