An ultra-narrow linewidth solution-processed organic laser

Area of Science:

• Photonics
• Materials Science
• Laser Physics

Background:

• Optically pumped thin-film lasers offer low cost and tunability for applications like sensing and spectroscopy.
• Existing thin-film lasers have broad linewidths (≥0.1 nm) due to short photon cavity lifetimes, limiting high-resolution applications.
• Narrow linewidths are crucial for advanced spectroscopic techniques and coherent sensing.

Purpose of the Study:

• To demonstrate a novel compact solid-state laser architecture for achieving ultra-narrow linewidths in thin-film lasers.
• To overcome the limitations of short photon cavity lifetimes in conventional resonator designs.
• To enable high-resolution spectroscopy and coherent sensing with thin-film laser technology.

Main Methods:

• A vertical external cavity laser design incorporating a holographic volume Bragg grating for spectral selection and output coupling.
• Utilizing solution-processed thin-film gain media within the compact laser structure.
• Employing short-pulse (0.4 ns) and longer (20 ns) optical pumping to investigate linewidth reduction.

Main Results:

• Achieved Fourier-transform-limited laser pulses with a linewidth of 900 MHz (1.25 pm) under short-pulse pumping.
• Reduced linewidth to 200 MHz (0.26 pm) using longer pump pulses, achieving a coherence length of 1 m.
• Demonstrated a compact laser design (∼cm³) with potential for tunability and transferability to various thin-film gain media.

Conclusions:

• The novel vertical external cavity laser with a holographic grating significantly narrows linewidths in thin-film lasers.
• This compact design offers an unprecedented coherence length, surpassing previous limitations.
• The technology presents a promising, compact alternative to traditional bulky grating systems for tunable lasers.