Repasky Kevin S, Nehrir Amin R, Hawthorne Justin T, Switzer Gregg W, Carlsten John L
Department of Electrical and Computer Engineering, Cobleigh Hall, Room 610, Montana State University, Bozeman, Montana 59717, USA.
Appl Opt. 2006 Dec 10;45(35):9013-20. doi: 10.1364/ao.45.009013.
The continuous tuning range of an external-cavity diode laser can be extended by making small corrections to the external-cavity length through an electronic feedback loop so that the cavity resonance condition is maintained as the laser wavelength is tuned. By maintaining the cavity resonance condition as the laser is tuned, the mode hops that typically limit the continuous tuning range of the external-cavity diode laser are eliminated. We present the design of a simple external-cavity diode laser based on the Littman-Metcalf external-cavity configuration that has a measured continuous tuning range of 1 GHz without an electronic feedback loop. To include the electronic feedback loop, a small sinusoidal signal is added to the drive current of the laser diode creating a small oscillation of the laser power. By comparing the phase of the modulated optical power with the phase of the sinusoidal drive signal using a lock-in amplifier, an error signal is created and used in an electronic feedback loop to control the external-cavity length. With electronic feedback, we find that the continuous tuning range can be extended to over 65 GHz. This occurs because the electronic feedback maintains the cavity resonance condition as the laser is tuned. An experimental demonstration of this extended tuning range is presented in which the external-cavity diode laser is tuned through an absorption feature of diatomic oxygen near 760 nm.
通过电子反馈回路对外腔长度进行微小校正，可扩展外腔二极管激光器的连续调谐范围，以便在激光波长调谐时维持腔共振条件。在激光调谐时维持腔共振条件，可消除通常限制外腔二极管激光器连续调谐范围的模式跳变。我们展示了一种基于利特曼 - 梅特卡夫外腔配置的简单外腔二极管激光器的设计，在没有电子反馈回路的情况下，其测量的连续调谐范围为1 GHz。为了加入电子反馈回路，向激光二极管的驱动电流中添加一个小的正弦信号，使激光功率产生小的振荡。通过使用锁相放大器将调制光功率的相位与正弦驱动信号的相位进行比较，产生一个误差信号，并在电子反馈回路中用于控制外腔长度。通过电子反馈，我们发现连续调谐范围可扩展到超过65 GHz。这是因为在激光调谐时电子反馈维持了腔共振条件。本文给出了这种扩展调谐范围的实验演示，其中外腔二极管激光器通过双原子氧在760 nm附近的吸收特性进行调谐。
