A sensitive near-field microscope for thermal radiation

Abstract

A scattering-type scanning near-field optical microscope in long-wavelength infrared (LWIR) region is developed by using an extremely sensitive detector, called the charge-sensitive infrared phototransistor. A tungsten probe attached to a quartz tuning fork is controlled in shear-force mode. Evanescent wave at a sample surface is periodically scattered by slowly (2 Hz) modulating the probe in the direction normal to the sample surface. Near-field microscopy of thermal LWIR radiation from room-temperature Au/GaAs gratings is demonstrated without using any external illumination or excitation. Achieved spatial resolution is better than 300 nm.

Near-Field Thermal Radiation: Recent Progress and Outlook

“…They concluded that the contribution to the EM-LDOS is dominated by SPhP on SiC at d = 200 nm but by SPP on gold at a larger distance of 3 µm, demonstrating spatial coherence effects of near-field thermal emission from thermally excited surface plasmons without any external illumination. Kajihara et al [153] demonstrated a spatial resolution of 300 nm by measuring thermal emission from gold plasmonic gratings. A charge-sensitive infrared phototransistor was used for probing the scattered long-wavelength infrared radiation near 15 µm wavelength [153].…”

“…Kajihara et al [153] demonstrated a spatial resolution of 300 nm by measuring thermal emission from gold plasmonic gratings. A charge-sensitive infrared phototransistor was used for probing the scattered long-wavelength infrared radiation near 15 µm wavelength [153]. Similarly, Kittel et al [154] showed the near-field thermal imaging from nanostructured surfaces by measuring the near-field LDOS of thermally excited electromagnetic waves at nanometer distances from the sample surface.…”

Charge-Sensitive Infrared Phototransisotrs: Ultra-sensitive Detectors in the Wavelength Range of 5-50µm

“…The [27] value of D * for CSIP is much higher than 300K-photonnoise limited performance, which will meet the requirements for high-resolution real-time passive imaging of RT small objects, e.g., living bio-cells. Recently CSIPs have been applied to the construction of a highly sensitive passive microscope [31,32].…”

Apertureless near-field microscopy using a knife blade as a scanning probe at millimeter wavelengths

“…16,[22][23][24] At higher frequencies than millimeter waves, especially in the terahertz and infrared regions, possibly due to the lack of low-loss waveguides, a sharp metal tip is widely used as a scanning probe. 23,[25][26][27][28][29][30][31][32][33][34][35] In this microscopy format, the metal tip is held close to the surface of the sample and evanescent waves are converted to propagating waves. The radiation scattered from the incident radiation is measured for imaging.…”