VCSEL wavelength tunability using controlled mechanical strain

Vertical-Cavity Surface-Emitting Lasers (VCSELs) have gained prominence in data centers due to their cost-efficiency and low-power modulation. Recent studies showed the possibility of changing output properties of VCSEL via anisotropic strain along the crystallographic axes, Polarization switching [1], polarization chaos [2] and even wavelength tuning by modifying the structure of the VCSEL [3].
In our study, we apply controlled mechanical strain to precisely tune the wavelengths of an array of off-the-shelf 1550nm VCSEL chips using a four-point bending module. This strain induces changes in refractive indices along crystallographic axes via the elasto-optic effect, resulting in birefringence changes within our VCSELs. We investigate the relationship between mechanical strain, birefringence, and wavelength. Varying the strain level produces a consistent wavelength shift of up to 1 nm for different current values, displaying a fairly linear correlation.
Our demonstration enhances our comprehension of VCSEL behavior and opens new avenues for optical communication applications.

[1] - Panajotov et al. Applied Physics Letters 77, 1590 (2000)
[2] - T. R. Raddo et al. Scientific Reports. 7, 14032 (2017)
[3] - Jin-Wei Shi et al. Optics Letters Vol. 45, No. 17 (2020)