Experimental method for high-accuracy reflectivity-spectrum measurements

Area of Science:

• Optics and Photonics
• Materials Science
• Semiconductor Devices

Background:

• Accurate characterization of optical components is crucial for laser performance.
• Distributed Bragg reflectors (DBRs) are essential for high-reflectivity mirrors in lasers.
• Existing methods may lack precision or be susceptible to noise and intensity fluctuations.

Purpose of the Study:

• To present a novel experimental method for precise measurement of mirror reflectivity spectra.
• To demonstrate the method's effectiveness in characterizing DBRs for optoelectronic devices.
• To provide accurate optical parameters for DBRs used in vertical-cavity surface-emitting lasers (VCSELs).

Main Methods:

• Utilizes multiple beam reflections between two identical mirrors for noise reduction.
• Employs single-mode optical fibers to ensure high optical beam quality.
• Incorporates high immunity against variations in optical beam intensity.

Main Results:

• Successfully characterized a 30-period GaAs/Al(0.65)Ga(0.35)As DBR.
• Measured a peak reflectivity of 99.43 ± 0.04% at 1.562 µm.
• Derived an optical absorption coefficient of α = 36 ± 6 cm⁻¹ and calculated internal reflectivity of 98.87 ± 0.12%.

Conclusions:

• The developed experimental method offers accurate reflectivity spectrum measurements.
• The characterized DBR is suitable for high-performance long-wavelength VCSEL applications.
• The method provides critical data for optimizing DBR design and laser performance.