Method and apparatus for creating a microscopic sample image of a molecular vibrational response of a sample

Abstract

A microscopic imaging method for creating a microscopic sample image (A) of a sample () comprises the steps of arranging the sample () on a sampling crystal (); irradiating the sample () with excitation laser pulses () and generating sample response pulses () with a sample response field as a result of an interaction of the excitation laser pulses () with the sample (); irradiating the sampling crystal () with probe laser pulses () being temporally synchronized with the excitation laser pulses () and spatially overlapped with the sample response pulses () in the sampling crystal (), wherein the probe laser pulses () have a shorter wavelength than the excitation laser pulses (); detecting the sample response field by electric-field sampling with the sampling crystal (), using the sample response pulses () and the probe laser pulses (); and calculating the sample image (A) based on the detected sample response field, wherein the excitation laser pulses () have a wavelength in a range from mid-infrared to visible light and the sample response pulses () are created by a coherent interaction process induced in the sample () and with a fixed phase relationship relative to the excitation laser pulses (), the sampling crystal () is a non-centrosymmetric crystal, the irradiating step is repeated at multiple sample points (A), wherein at each sample point (A) the irradiating steps are successively repeated with multiple temporal probe delays of the probe laser pulses () relative to the excitation laser pulses (), at each probe delay, a sum or difference frequency pulse () of a sample response pulse () and a probe laser pulse () is generated, and at each probe delay, a spectral interference pulse () is created by a spectral interference of the sum or difference frequency pulse () and the current probe laser pulse, the detecting step includes sensing a polarization state of the spectral interference pulse () by an ellipsometer device () at each probe delay, wherein the local sample response field at the sample point (A) is derived from the polarization states sensed at all probe delays, and the sample image (A) is calculated based on the sample response field detected at the sample points (A). Furthermore, a microscopic imaging apparatus is described.