Laser Tuning in Layered h-BN Crystals

Area of Science:

• Photonics and Optical Engineering
• Materials Science
• Condensed Matter Physics

Background:

• Integrated optics is crucial for advanced optical communication, sensors, and computing.
• Tunable laser technology is essential for on-chip optical integration.
• Raman scattering facilitates energy conversion from photons to optical phonons via photon-phonon interaction.

Purpose of the Study:

• To investigate hexagonal boron nitride (h-BN) as an energy conversion medium for tunable lasers.
• To explore the potential of h-BN in achieving on-chip optical integration through Raman scattering.
• To demonstrate continuous wavelength tuning of scattered light in h-BN.

Main Methods:

• Utilized angle-resolved polarized Raman spectroscopy.
• Employed hexagonal boron nitride (h-BN) as the Raman scattering medium.
• Investigated the effect of laser polarization relative to the c-axis.
• Performed measurements across a temperature range of 80–420 K.

Main Results:

• Maximal Raman scattering and minimal depolarization ratio were observed when the laser polarization vector (e) was perpendicular to the c-axis.
• At room temperature, h-BN produced a 522.8 nm signal with a 0.24 nm FWHM under 488 nm excitation.
• A high-precision wavelength shift of 0.006 nm/25 K was achieved within the 80–420 K temperature range.

Conclusions:

• Hexagonal boron nitride is a viable material for tunable laser applications in integrated optics.
• Angle-resolved polarized Raman spectroscopy effectively characterizes the optical properties of h-BN.
• Continuous wavelength tuning of scattered light in h-BN was successfully demonstrated, paving the way for on-chip optical integration.