Towards Low-Temperature Optical Investigations of Diamond Color Centers

Mondal, Abir (2025) Towards Low-Temperature Optical Investigations of Diamond Color Centers. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS Dissertation of Abir Mondal (20MS044)) 20MS044_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (5MB)

Abstract

This thesis presents the development and characterization of an experimental platform aimed at studying diamond color centers at cryogenic temperatures. Central to the work is the implementation of a multifunction data acquisition (DAQ) system, for both signal readout and pulse generation. A fully DAQ-based control interface was developed in Python, enabling synchronized acquisition of photoluminescence (PL) and reference signals, along with precise digital timing for experimental sequences. In parallel, a detailed spectroscopic analysis of the diamond sample was performed from room temperature down to 4 K. Emission spectra revealed the presence of NV−, NV0 and SiV centers, along with characteristic Raman features. The thermal evolution of zero-phonon lines (ZPLs) was analyzed in terms of peak position and linewidth. A systematic redshift and broadening with increasing temperature were observed, with SiV centers showing greater sensitivity. Notably, non-monotonic behavior in ZPL shift was observed below 50 K. The spin-lattice relaxation time T1 of NV− centers was measured using an all-optical pulsed protocol. Careful normalization techniques were applied to correct for laser power drift, and appropriate experimental parameters were chosen based on time-resolved PL dynamics. The extracted relaxation profile was well-described by a single exponential decay, consistent with spin-lattice coupling mechanisms. In essence, these results demonstrate a versatile, and programmable experimental approach to probing the optical and spin dynamics of solid-state color centers, with implications for quantum sensing and information applications.

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