Laser light source and photoelectron microscope

A photoemission electron microscope comprising:

• a laser light source configured to emit a coherent light to irradiate a measurement sample;
• an irradiation lens system configured to focus the coherent light from the laser light source onto a surface of the measurement sample;
• a controller configured to control level of the coherent light;
• and
• a driving mechanism configured to move a position of an irradiation spot of the coherent light on the surface of the measurement sample, wherein
• the laser light source comprises:
• a first laser light source configured to emit a continuous wave coherent light;
• an optical resonator including an optical path in which the continuous wave coherent light is configured to circulate and including a non-linear optical element disposed on the optical path;
• and
• a quasi-continuous wave light source configured to emit a quasi-continuous wave coherent light having a wavelength shorter than that of the continuous wave coherent light and having a near rectangular output waveform, wherein
• when the quasi-continuous wave coherent light is incident on the non-linear optical element from outside the optical resonator while the continuous wave coherent light is entering the optical resonator to circulate in the optical path, the coherent light having a wavelength shorter than that of the quasi-continuous wave coherent light is configured to be emitted from the non-linear optical element, and
• the controller is configured to cause the coherent light to be in a high level during shooting with the photoemission electron microscope and to be in a low level at least when the driving mechanism moves the position of the irradiation spot of the coherent light on the surface of the measurement sample.