| 摘要 |
PURPOSE:To realize an inexpensive unit while enabling the easy control of a pulse width, by arranging a 1/4 wavelength plate in series with an electro-optical element between a double refraction element and a total reflection mirror. CONSTITUTION:An incident light L3 entering into a 1/4 wavelength plate 6 goes out as a light L4, which has been circularly polarized counterclockwise. A phase of lambda/4 is further applied thereto by an electro-optical element 3. As a result, a light L5 applied to a reflection mirror 1 has a plane of polarization rotated by 90 deg. with respect to that of the incident light L3. When a light L6 reflected by the total reflection mirror 1 enters into the electro-optical element 3 in the opposite direction, it is again circularly polarized counterclockwise. A phase difference of lambda/4 is applied thereto by the 1/4 wavelength plate 6. Accordingly, a light L7 returning to a double refraction element 4 has the same plane of polarization with the incident light L3. If the application lambda/4 voltage to the electro-optical element 3 is stopped, the returning light L7 becomes an extraordinary ray in the double refraction element 4, and it goes along an optical path P and returns as a randomly polarized light L. Thus, the resonance conditions of a resonator are satisfied, realizing high Q, and the laser is caused to oscillate. |
