A He-Ne gas laser with tunable wavelength and stable output intensity based on photon tunneling

In this paper, we report on a wavelength modulation He-Ne gas laser with stable output intensity. Wavelength modulation of the laser is achieved by modulating the length of the resonator cavity. And photon tunneling is used to change the loss of the cavity, namely, to modulate the laser output intensity. Then, the closed-loop feedback control technique is adopted to ensure the output intensity is stable when the laser wavelength is being modulated. Photon tunneling shows a significant control effect on the output light intensity of the laser. Finally, compared to a laser without feed-back control, the output stability of the wavelength modulation laser with feed-back control is an order higher in magnitude than that of the former, as average standard deviation of the output intensity decreases to a thirtieth of the original. In addition longitudinal mode characteristics and beam quality of the laser is measured. The measuring results show that it has two longitudinal modes and an excellent beam quality as the value of M2 factor is 1.029.