Intra-cavity frequency-doubled mode-locked semiconductor disk laser at 325 nm

Area of Science:

• Optics and Photonics
• Semiconductor Lasers
• Quantum Dot Technology

Background:

• Semiconductor disk lasers (SDLs) offer scalable power and wavelength flexibility.
• Intra-cavity second harmonic generation (SHG) is a common technique for generating shorter wavelengths.
• Quantum dots (QDs) are promising materials for laser gain and saturable absorption due to their tunable optical properties.

Purpose of the Study:

• To develop a passively mode-locked semiconductor disk laser (SDL) for efficient generation of ultraviolet (UV) light.
• To investigate the use of InP quantum dots (QDs) in both the gain and saturable absorber for UV generation.
• To achieve pulsed UV laser emission through intra-cavity second harmonic generation.

Main Methods:

• A v-shaped cavity configuration was employed, utilizing semiconductor samples as end mirrors.
• A beta barium borate (BBO) crystal was integrated for second harmonic generation.
• InP quantum dots (QDs) were used as the active material in both the gain and saturable absorber structures.
• Passively mode-locking was achieved using a semiconductor saturable absorber mirror (SESAM).

Main Results:

• The laser successfully emitted at 650nm (fundamental) and generated UV light via SHG.
• Autocorrelation measurements at 650nm indicated a pulse duration of 1.22 picoseconds (ps).
• The laser achieved an average output power of 10mW per beam at 650nm and 0.5mW at 325nm with a repetition frequency of 836MHz.

Conclusions:

• A passively mode-locked SDL with intra-cavity SHG was successfully demonstrated for UV generation.
• The use of InP QDs in both gain and absorber is effective for pulsed UV laser emission.
• The results show potential for compact and efficient UV laser sources based on SDL technology.