Radiation pressure excitation of a low temperature atomic force/magnetic force microscope for imaging in 4-300 K temperature range

Abstract

We describe a novel radiation pressure based cantilever excitation method for imaging in dynamic mode atomic force microscopy (AFM) for the first time. Piezo-excitation is the most common method for cantilever excitation, however it may cause spurious resonance peaks. Therefore, the direct excitation of the cantilever plays a crucial role in AFM imaging. A fiber optic interferometer with a 1310 nm laser was used both for the excitation of the cantilever at the resonance and the deflection measurement of the cantilever in a commercial low temperature atomic force microscope/magnetic force microscope (AFM/MFM) from NanoMagnetics Instruments. The laser power was modulated at the cantilever's resonance frequency by a digital Phase Locked Loop (PLL). The laser beam is typically modulated by ∼500 μW, and ∼141.8 nm oscillation amplitude is obtained in moderate vacuum levels between 4 and 300 K. We have demonstrated the performance of the radiation pressure excitation in AFM/MFM by imaging atomic steps in graphite, magnetic domains in CoPt multilayers between 4 and 300 K and Abrikosov vortex lattice in BSCCO(2212) single crystal at 4 K for the first time.

Control of quality factor of atomic force microscopy cantilever by cavity optomechanical effect

“…Therefore, controlling the effective Q factor necessitates changing the slope either by changing the cavity length or the optical power. The dual-laser scheme has the following advantage compared to the optical cantilever excitation scheme with only a single laser 18) and is critical to the effective Q factor modulation technique presented here. Because the detection (1550 nm) laser is dedicated solely to detection, it does not need to be modulated for the cantilever excitation.…”

“…The AC component of the reflected detection laser power directly reflects the cantilever oscillation, and there is no need to subtract the modulation signal unlike in a single laser setup where a single laser is used for both detection and excitation. 18) Additionally, we can vary the average (DC) intensity of the excitation (1310 nm) laser by varying the DC component of the modulation signal which is applied to the laser current driver. This permits us to vary the optomechanical spring force which is caused by the excitation (1310 nm) laser without changing the deflection measurement sensitivity.…”

Photon force microelectromechanical system cantilever combined with a fibre optic system as a measurement technique for optomechanical studies

“…At the microscale, radiation pressure (RP) supports many important technologies such as optical tweezers (object trapping) [9,10], optical cooling [11,12] and high-power laser emission measurement [13][14][15]. Although the obtained results have been impressive and noticeable, the measurement procedures were using time-consuming and increased the uncertainty calibration process, for example when using a cantilever as a force sensor, determination of the spring constant is needed [16]. Another approach is to calibrate the spring constant parameter with the use of a known, i.e.…”