在精密测量领域, HeNe激光器是制造激光干涉仪的首选.但能够产生中频差4-40 MHz的双折射-塞曼双频HeNe激光器的频差是随机的,小到几百kHz,大到十几MHz.为了让频差能够满足制作双频激光干涉仪的要求,曾出现过弹性加力法、钻孔应力调节法等调整和频差赋值的方法.但这些方法在实际应用中都不是很理想.采用激光内雕法赋值频差,通过在激光器的平面输出镜内部雕刻出不同图案,使平面镜内部产生满足要求的相位延迟,达到为频差赋值的目的.激光内雕法有很多优点：不损害激光器,美观；功率损失小,出光强度可接近原始光强度；可反复赋值,频差在0-60 MHz范围内可调整；频差的稳定性好,采用稳频措施后频差的波动范围小于每小时10 kHz.%In the field of precision measurement, HeNe laser is the first choice for fabricating laser interferometer. But the frequency difference of Birefringence-Zeeman dual-frequency HeNe laser, which can produce a medium frequency difference of 4-40 MHz, is randomly from as small as hundreds of kHz to as large as a dozen of MHz. To meet the production requirements for frequency difference of dual-frequency laser interferometer, there are some methods such as elastic strength and hole-drilling stress adjustment. But in the practical application, these methods are not very satisfactory. Laser-micro-engraving method assigns frequency difference by engraving a pattern in the plane mirror, and causes the phase retardation to achieve the purpose of frequency difference assignment. Laser engraving technique has many advantages: harmless to the laser, beauty, low power loss. The output power is close to the original light intensity. The frequency difference can be repeatedly adjusted and is stable. By frequency stabilization, the frequency difference fluctuates in a range of less than 10 kHz per hour.
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