Optical–Microwave Pump–Probe Studies of Electronic Properties in Novel Materials

• Published in: physica status solidi (b) Vol. 257; no. 12
• Main Authors: Kollarics, Sándor, Bojtor, András, Koltai, Kristóf, Márkus, Bence Gábor, Holczer, Károly, Volk, János, Klujber, Gergely, Szieberth, Máté, Simon, Ferenc
• Format: Journal Article
• Language: English
• Published: 01-12-2020
• Subjects: coplanar waveguides; microwave-detected photoconductivity decay; nitrogen-vacancy centers; optically detected magnetic resonance
• ISSN: 0370-1972; 1521-3951
• DOI: 10.1002/pssb.202000298

Combined microwave–optical pump–probe methods are emerging to study the quantum state of spin qubit centers and the charge dynamics in semiconductors. A major hindrance is the limited bandwidth of microwave irradiation/detection circuitry which can be overcome with the use of broadband coplanar waveguides (CPWs). The development and performance characterization of two spectrometers is presented as follows: an optically detected magnetic resonance spectrometer (ODMR) and a microwave‐detected photoconductivity measurement. In the first method, light serves as detection and microwaves excite the investigated medium, whereas in the second, the roles are interchanged. The performance is demonstrated by measuring ODMR maps on the nitrogen‐vacancy (NV) center in diamond and time‐resolved photoconductivity in p‐doped silicon. The results demonstrate both an efficient coupling of the microwave irradiation to the samples as well as an excellent sensitivity for minute changes in sample conductivity.
The design and properties of two spectrometers based on coplanar waveguides are presented. The performance of the optically detected magnetic resonance (ODMR) spectrometer is demonstrated by measuring ODMR maps on nitrogen‐vacancy centers in diamond, whereas the time‐resolved microwave‐detected photoconductivity decay setup is put to the proof with p‐doped silicon samples.