Laser light source and photoelectron microscope

Patent metadata

Field	Value
Publication number	US-12332196-B2
Application number	US-202017615814-A
Country	US
Kind code	B2
Filing date	Jun 1, 2020
Priority date	Jun 3, 2019
Publication date	Jun 17, 2025
Grant date	Jun 17, 2025

Abstract

A laser light source for a photoemission electron microscope for emitting a coherent light includes: 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. 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 emitted from the non-linear optical element.

First claim

The invention claimed is:

1. 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.

2. The photoemission electron microscope according to claim 1 , further comprising:
an energy analyzer configured to disperse photoelectrons emitted from the measurement sample according to energy of the photoelectrons; and
an electron beam detector configured to detect a part of the photoelectrons with a certain energy based on dispersion in the energy analyzer.

3. The photoemission electron microscope according to claim 1 , wherein
the non-linear optical element is CLBO or β-BBO.

4. The photoemission electron microscope according to claim 1 , wherein
the continuous wave coherent light has a wavelength of 750 nm to 2100 nm.

5. The photoemission electron microscope according to claim 1 , wherein
the quasi-continuous wave coherent light has a wavelength of 210 nm to 360 nm.

6. The photoemission electron microscope according to claim 1 , wherein
the quasi-continuous wave light source comprises:
a second laser light source configured to emit a continuous wave coherent light; and
an optical modulator configured to modulate an output waveform of the continuous wave coherent light emitted from the second laser light source into the near rectangular output waveform.

7. The photoemission electron microscope according to claim 1 , wherein
the quasi-continuous wave light source comprises a second laser light source configured to emit a continuous wave coherent light on and off repeatedly to generate the quasi-continuous wave coherent light.

8. The photoemission electron microscope according to claim 1 , wherein
the quasi-continuous wave light source is controlled such that timing at which an output of the laser light source becomes a high level is synchronized with timing of shooting with the photoemission electron microscope.

9. The photoemission electron microscope according to claim 1 , wherein
the quasi-continuous wave coherent light has a duty cycle of 50% or less.

10. The photoemission electron microscope according to claim 1 , wherein
a peak power of the quasi-continuous wave coherent light is 1 W or more.

11. The photoemission electron microscope according to claim 1 , wherein
the quasi-continuous wave light source is wavelength tunable.

12. The photoemission electron microscope according to claim 1 , wherein
the quasi-continuous wave light source includes a wavelength-tunable titanium-sapphire laser and is configured to generate the quasi-continuous wave coherent light from a second harmonic wave or a third harmonic wave of the wavelength-tunable titanium-sapphire laser.

13. The photoemission electron microscope according to claim 6 , wherein
the second laser light source is configured to perform a multi-mode oscillation of the continuous wave coherent light.

Assignees

• Univ Tokyo
• Oxide Corp

Inventors

• Shin Shik
• Taniuchi Toshiyuki
• Imai Shinichi
• Fujiura Kazuo
• Furukawa Yasunori

Classifications

• H01S3/0092

  Nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser cavity (nonlinear frequency conversion per se G02F1/35) · CPC title

• H01S3/0816

  having 4 reflectors, e.g. Z-shaped resonators · CPC title

• G02F1/353 Primary

  Frequency conversion, i.e. wherein a light beam is generated with frequency components different from those of the incident light beams · CPC title

• G02B21/06

  Means for illuminating specimens · CPC title

• G01N2223/33

  scanning, i.e. relative motion for measurement of successive object-parts · CPC title