We report a novel single-frequency, injection-locked vertical external-cavity surface-emitting laser (VECSEL) for the first time to the best of our knowledge. The wavelength of the injection locked output can be tuned with the master laser. A lower power single-frequency VECSEL served as the master oscillator that provides wavelength tunability with frequency selective elements such as a birefringent filter, and/or an etalon. The master laser is mode-matched to the slave VECSEL ring resonator. By varying the injecting power and wavelength of the master VECSEL oscillator, we investigated the locking ability of the laser. With 200 mW of the injection power, we generated above 4 W of stable output in single frequency. With the ability to provide narrow linewidth, good beam quality, and stable output with sufficient power at specific wavelengths, such laser sources can be useful in many laser applications, such as precision spectroscopy.
Keywords: VECSEL, OPSL, semiconductor laser, single frequency, injection-locking
Many studies, such as atom trapping1, 2 and atomic spectroscopy3, require narrow linewidth laser sources at specific wavelength. For example, the 61S0-63P1 transition of Hg is at 253.7 nm. The atomic trapping laser source can be realized by a frequency quadrupled 1014.9 nm laser. For this case, the wavelength is not reachable with conventional bulk solid-state lasers or fiber-based laser sources. Vertical external-cavity surface-emitting lasers (VECSELs), on the other hand, provide the possibility to tailor the desired wavelength through bandgap engineering and wafer growth. VECSELs could generate near diffraction limited output by pumping the TEM00 mode area given by the external cavity. Mode selection elements can be inserted to enforce single-frequency operation. Fine tuning can be accomplished by adjusting the cavity length with piezoelectric actuator. Moreover, VECSELs could generate watts level of output power. The output power is scalable with different pump spot sizes to some extent4, 5. These advantages above make VECSELs to be one of the best candidates for such applications.
This work realized the high power, single-frequency output in good quality laser beam at a tailored wavelength, opening up new applications where laser emission at specific wavelength is needed, such as precision spectroscopy. In the research, we will approach our goal with the injection-locking technique. The wavelength of the injection locked output can be tuned with the master laser. A lower power single-frequency VECSEL serves as the master laser that provides wavelength tunability by inserting frequency selective elements such as a birefringent filter, and/or an etalon. The master laser is mode-matched to a slave VECSEL ring resonator, and the lasing frequency of the slave laser is enforced to that of the injected signal, by matching the resonant frequency of the slave laser cavity to the injected signal using a servo loop....