Spectral shaping of a broadband multimode diode laser using a virtually imaged phased array

Broadband laser sources are fundamental tools in a wide range of modern physics applications, such as high-resolution laser spectroscopy [1], surface topography on a sub-micrometric scale [2], and rovibrational optical pumping of molecules [3]. For creating rovibrational molecular dark states, these broadband sources must be shaped in a way that there is no light in states to be populated. However, for molecules with a lower rotational constant, a dispersion element with higher spectral resolution such as Virtually Imaged Phased Array (VIPA) must be used. In this work, we have built a high-resolution spectral shaping system, based on VIPA and a digital micromirror device (DMD), to manipulate a multimode diode laser spectrum. Due to its working principles, the system reduces the available optical power by ∼-27 dB. To overcome this limitation, we have seeded its output, using a double-pass configuration, in a tapered amplifier, to increase the available power to ∼60 mW. We have implemented spectral features with a resolution of 0.02 cm^-1. This may be attractive for an extensive number of applications, especially optical pumping in molecular physics.

[1] - Zhu, X., Lin, D., Hao, Z., Wang, L., & He, J. (2020). A VIPA Spectrograph with Ultra-high Resolution and Wavelength Calibration for Astronomical Applications. The Astronomical Journal, 160(3), 135.

[2] - Itakura, S., Uenohara, T., Mizutani, Y., & Takaya, Y. (2021). Fundamental study of surface topography measurement by broadband optical frequency comb scattering spectroscopy - Basic study of diffraction pattern spectroscopy by VIPA Spectrometer -. Measurement: Sensors, 18.

[3] - Viteau, M., Chotia, A., Allegrini, M., Bouloufa, N., Dulieu, O., Comparat, D., & Pillet, P. (2008). Optical pumping and vibrational cooling of molecules. Science, 321(5886), 232–234.