Chip-integrated extended-cavity mode-locked laser in the visible

Area of Science:

• Photonics and Laser Technology
• Integrated Optics
• Semiconductor Lasers

Background:

• Mode-locked lasers are crucial for advanced applications like biological imaging and single-photon generation.
• Previous chip-integrated mode-locked lasers were limited to the infrared spectrum due to propagation loss and alignment challenges in visible light.
• Realizing visible-spectrum chip-integrated lasers requires overcoming significant fabrication and integration hurdles.

Purpose of the Study:

• To demonstrate the first chip-integrated mode-locked diode laser operating in the visible spectrum.
• To overcome the limitations of propagation loss and alignment tolerances in visible-light integrated photonics.
• To enable new applications requiring compact, visible-spectrum ultrashort pulse sources.

Main Methods:

• Utilized a gallium arsenide (GaAs) gain chip integrated with a low-loss silicon nitride (SiN) photonic circuit for cavity extension.
• Employed a saturable absorber (SA) fabricated by focused ion beam (FIB) milling for passive mode-locking.
• Designed an integrated photonic circuit to facilitate cavity extension and stable laser operation.

Main Results:

• Successfully demonstrated a chip-integrated mode-locked diode laser at a center wavelength of 642 nm.
• Achieved an average output power of 3.4 mW.
• Observed a spectral bandwidth of 1.5 nm with a repetition rate of 7.84 GHz.

Conclusions:

• This work presents the first chip-integrated mode-locked diode laser in the visible range.
• The integrated photonic circuit approach effectively extends the cavity and enables passive mode-locking.
• The demonstrated laser paves the way for miniaturized visible light sources for diverse scientific and technological applications.