研究目的
To propose and demonstrate a way to modulate the coherent phonon emission from OM crystals by a photothermal effect induced by an external laser, effectively creating a phonon switch working at ambient conditions of pressure and temperature.
研究成果
The study demonstrates the possibility to locally address a single OM cavity and modulate its coherent phonon emission. This feature will become increasingly important in the future, as the number of phonon emitters per unit area will increase. The method is tailored specifically for the phonon lasing scheme of this work and is valid at ambient temperature and pressure conditions.
研究不足
The modulation speed is limited by the build-up time of the mechanical motion of the OM structure. The power required for modulation is less than 3% of that used to reach the phonon lasing regime.
1：Experimental Design and Method Selection:
The study involves the use of OM crystals fabricated from a silicon-on-insulator wafer, characterized by evanescent light coupling into the cavity from a tapered fibre at room-temperature and atmospheric pressure. The driving laser is an infrared (IR) laser with tunable wavelength in the range of 1440–1640 nm and power up to 20 mW. An 808 nm continuous-wave solid-state laser is used as an external optical pump to switch between the different states of the OM crystal.
2：Sample Selection and Data Sources:
The OM crystal used in this study is fabricated from a silicon-on-insulator wafer (resistivity ρ ～1-10 ? cm?1, p-doping of ～1015 cm?3). The top silicon layer and buried oxide layer have thicknesses of 220 nm and 2 μm, respectively.
3：3). The top silicon layer and buried oxide layer have thicknesses of 220 nm and 2 μm, respectively.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: The structures were patterned in a 100 nm thick PMMA resist layer with electron-beam lithography and transferred to the silicon layer by reactive ion etching. The oxide layer was subsequently removed with buffered hydrofluoric acid to release the OM crystal.
4：Experimental Procedures and Operational Workflow:
The OM structures are characterized by evanescent light coupling into the cavity from a tapered fibre at room-temperature and atmospheric pressure. The driving laser passes through a polarization controller before being coupled to a tapered microlooped fibre. The signal is then detected by a InGaAs detector of bandwidth 12 GHz and transmitted to a signal analyser with a bandwidth of 13.5 GHz.
5：5 GHz.
Data Analysis Methods:
5. Data Analysis Methods: The mechanical spectrum is obtained by processing the transmitted optical signal with a spectrum analyser.
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