Tuning of external-cavity semiconductor lasers with chirped diffraction gratings

Area of Science:

• Optics and Photonics
• Semiconductor Lasers
• Diffractive Optics

Background:

• External cavity semiconductor lasers are crucial for tunable wavelength applications.
• Conventional tuning methods often rely on rotating gratings, which can be complex.
• Developing simpler and more efficient tuning mechanisms is an ongoing research area.

Purpose of the Study:

• To introduce a novel tunable semiconductor laser scheme.
• To investigate the wavelength tuning properties of chirped gratings in an external cavity.
• To demonstrate a simplified tuning mechanism independent of wavelength-dependent beam steering.

Main Methods:

• Fabrication of a chirped grating using holographic interference of two Gaussian beams with different radii of curvature.
• Integration of the chirped grating into an external cavity semiconductor laser configuration (Littrow configuration).
• Experimental investigation of wavelength tuning by translating the chirped grating.

Main Results:

• The chirped grating enabled wavelength selection through linear translation, eliminating the need for rotation.
• The external cavity configuration provided a tunable output beam with a wavelength-independent propagation angle.
• Successful tuning of both visible and infrared diode lasers across a broad spectral band.

Conclusions:

• The proposed chirped grating external cavity laser offers a simplified and effective method for tunable wavelength generation.
• This approach provides wavelength tunability with a constant output beam angle, advantageous for system integration.
• The technique is applicable to various semiconductor laser types, demonstrating its versatility.