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1.
Distortion of optical feedback signals in microchip Nd:YAG lasers subjected to external multi-beam interference feedback 下载免费PDF全文
This paper proposes a theoretical analysis for the
characteristics of an external cavity Nd:YAG laser with feedback of
multiple-beam interference, which is induced by the multi-reentrance
of the light from the external Fabry--Perot cavity. The theoretical
model considers the multiple beam interference of the external
Fabry--Perot cavity. It is found that the optical feedback signals
are distorted to pulse waveforms instead of the sinusoidal ones in
conventional feedback. The experimental results are in good
agreement with the theoretical analysis. The obtained theoretical
and experimental results can advance the development of a laser
feedback interferometer. 相似文献
2.
This paper investigates the intensity tuning characteristics of a double
longitudinal modes He--Ne laser subjected to optical feedback. The intensity
undulations of the total light and the two modes are observed for different external
cavity length. Two modulations of the internal cavity length are performed. One is
only for the internal cavity length being modulated and the other is for both the
internal and the external cavity length being modulated. The undulation frequency of
the total light is found to be determined by the ratio of external cavity length to
internal cavity length in both modulations. When the external cavity length is
integral times of the internal cavity length, the fringe frequency of the total
light could be seven or even more times of that in conventional optical feedback. A
simple theoretical analysis is presented, which is in good agreement with the
experimental results. The potential use of the experimental results is also
discussed. 相似文献
3.
Intensity modulation characters of orthogonally polarized HeNe lasers with different optical feedback level 下载免费PDF全文
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
4.
A simple and precise retardation measurement based on laser feedback is demonstrated. The measurement principle is based on polarization flipping induced by optical feedback from an external birefringence cavity. The measured wave plate is located in the external cavity. When the length of the external cavity is tuned, the polarization states of laser will flip between two eigenstates, and the position of polarization flipping in one period of intensity modulation will vary with retardation of the wave plate. The duty ratio of two eigenstates is used to determine the retardation. Main advantages of the technique are that it is compact, low cost, fast and flexible. Especially, it is insensitive to a fluctuation of laser intensity and is suitable for on-line measurement. The experimental results have shown that the measurement uncertainty is better than 0.03° in the range 30°-150°. 相似文献
5.
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
6.
Influence of Optical Feedback from Birefringence External Cavity on Intensity Tuning and Polarization of Laser 总被引:1,自引:0,他引:1 下载免费PDF全文
The characteristics of intensity tuning and polarization of He-Ne laser with optical feedback are studied. When the internal cavity length of the laser with birefringence optical feedback is tuned, not only does output intensity vary with laser frequency, but also the polarization periodically hops between two orthogonal directions. If the phase difference of birefringence is π/2, two polarization states Mternately oscillate and have equal bandwidths within the longitudinal mode spacing. The times of polarization flipping in the longitudinal mode bandwidth is proportional to the ratio of external cavity length to internal cavity length. The experimental results are explained, and the potential uses are also discussed. 相似文献
7.
The modes competition characteristics in birefringence cavity laser are studied in different regions of the gain curve. The mode's intensity modulation depth with modes competition is much deeper than that without modes competition. When the average intensities of the two modes are comparable, the intensity modulation depth of either mode reaches its maximum. Modes competition can do more contribution to the mode's modulation depth than the percentage of light reflected back into the laser cavity does. These characteristics can be used to improve the sensitivity of an optical feedback system. A modes competition factor is introduced to either mode's intensity expression which describes the laser intensity more precisely. 相似文献
8.
We investigate the characteristics of intensity tuning in a single mode microchip Nd:YAG laser with an external cavity. The undulation of laser intensity in a period of A/2 change of the internal cavity length is observed. Two different optical feedback cases are performed. One is an external cavity reflector perfectly aligned and the other is an external cavity reflector tilted. However, the fluctuation frequency of laser intensity in a period of A/2 change of the internal cavity length in these two cases is found to be determined by the ratio of external cavity length to internal cavity length. Meanwhile, for the tilted external cavity, the fluctuation frequency is also related to multiple feedbacks in the tilted external cavity. 相似文献
9.
Optical feedback characteristics in a helium neon laser with a birefringent internal cavity 下载免费PDF全文
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
10.
Strong modes competition makes only one of o-light and e-light oscillate in a birefringent dual-frequency laser when the angle between the crystalline axis and the laser beam is nearly zero. When the oscillated mode is in a different part of the gain curve, the detected intensity curves of o-light and e-light are quite different in the existence of optical feedback. The curves are divided into five cases. Three cases of the experimental results can be used for direction discrimination. The polarization characteristics of the birefringent cavity He-Ne laser are also discussed without optical feedback. 相似文献
11.
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
12.
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
13.
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
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16.
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