An optically detected magnetic resonance spectrometer with tunable laser excitation and wavelength resolved infrared detection

Abstract

We present the development and performance of an optically detected magnetic resonance (ODMR) spectrometer. The spectrometer represents advances over similar instruments in three areas: (i) the exciting light is a tunable laser source which covers much of the visible light range, (ii) the optical signal is analyzed with a spectrograph, (iii) the emitted light is detected in the near-infrared domain. The need to perform ODMR experiments on single-walled carbon nanotubes motivated the present development and we demonstrate the utility of the spectrometer on this material. The performance of the spectrometer is critically compared to similar instruments. The present development opens the way to perform ODMR studies on various new materials such as molecules and luminescent quantum dots where the emission is in the near-infrared range and requires a well-defined excitation wavelength and analysis of the scattered light.

Improved Laser‐Based Photoluminescence on Single‐Walled Carbon Nanotubes

“…The usual CW pumped dye laser has an outcoming beam of about 2.25 mm diameter, which does not have an observable divergence after 1 m (this is the practical distance of our laser usage conditions). In contrast, the output beam diameter of the pulsed dye laser is about 6 mm, which diverges to about an 8 mm diameter size after 1 m. This is still a usable laser beam size for our spectrometer operation …”

“…In practice, one needed to use a set of “green‐optimized” (reflection >99.99 % for 500–670 nm) and “red‐optimized” (reflection >99.99% for 570–740 nm) lower‐ and upper‐folding mirrors depending on the working wavelength, due to the limited wavelength coverage of high‐reflection laser mirrors. The dye laser system was used in combination with a home‐built PL spectrometer which was described in the study by Negyedi et al…”

Incidence of Quantum Confinement on Dark Triplet Excitons in Carbon Nanotubes

“…The development of the ODMR instrument, which allows energy resolved excitation and detection in the near-infrared domain, was reported in ref ( 19 ). A tunable laser system, comprising a 532 nm laser (5 W) pumped Ti:Sa laser, enables tunable excitation of the SWCNTs, and emitted light is detected in a dispersive monochromator system (Horiba Jobin Yvon ihr320) using a liquid nitrogen cooled InGaAs detector in the 900–1500 nm range.…”

“…Here, we report the direct observation of the phosphorescence signal from the triplet levels in pristine SWCNTs in an ( n , m ) chiral index resolved manner. The key to this was the recent development of a unique ODMR spectrometer 19 which operates with a tunable laser source, thus selecting a particular absorption energy, and by analyzing the wavelength of the emitted signal under magnetic resonance conditions. Another challenge to overcome was the near-infrared emission range for most SWCNTs where the detector efficiency is lower.…”

Incidence of Quantum Confinement on Dark Triplet Excitons in Carbon Nanotubes

“…Here, we report the direct observation of the phosphorescence signal from the triplet levels in pristine SWCNTs in an (n, m) chiral index resolved manner. The key to this was the recent development of a unique ODMR spectrometer 19 which operates with a tunable laser source, thus selecting a particular absorption energy, and by analyzing the wavelength of the emitted signal under magnetic resonance conditions. Another overcome challenge was the near-infrared emission range for most SWCNTs where detector efficiency is lower.…”