High-speed binary laser beam shaping and scanning
A device and method are for shaping and scanning an ultrafast laser beam. The device includes a laser source configured to output a pulsed laser beam containing different frequency spectrum, a digital micromirror device (DMD) consisting of micromirrors, which are configured to receive the laser beam and shape the received laser beam with computer generated holograms, and a dispersion compensation unit, arranged before or after the DMD, which is configured to transfer the laser beam from the laser source to the DMD with a designated angular dispersion for neutralizing the first angular dispersion introduced by the DMD.
1. A device for shaping and scanning a pulsed laser beam containing a different frequency spectrum, comprising:
a digital micromirror device (DMD) consisting of a plurality of micromirrors, configured to receive the laser beam and shape the received laser beam with a binary hologram, wherein the DMD simultaneously functions as a programmable binary mask and a blazed grating;
a dispersion compensation unit, arranged before or after the DMD, including a blazed grating configured to disperse a spectrum of the laser beam so as to transfer the laser beam from the laser source to the DMD with a designated angular dispersion for neutralizing the angular dispersion introduced by the DMD; and
a lens pair comprising a first lens L 1 and a second lens L 2 , configured to collimate and expand the pulsed laser beam and image the beam onto the DMD, wherein the second lens L 2 has a focal length f L2 and is arranged between the DMD and the blazed grating, wherein a distance S G-L2 between the blazed grating and the lens L 2 and a distance S L2-D between the lens L 2 and the DMD satisfy the following equation set:
{
s
G
-
L
2
s
L
2
-
D
=
m
G
m
D
·
d
0
cos
θ
i
θ
d
0
cos
θ
m
θ
1
f
L
2
=
1
s
G
-
L
2
+
1
s
L
2
-
D
wherein m is an integer indicating a diffraction order, d is a grating period, θ i and θ m are incident and diffraction angles of a m th order diffraction, respectively, and G and D are the blazed grating and the DMD, respectively.
2. The device of claim 1 , wherein the dispersion compensation unit further comprises a mirror configured to change the sign of angular dispersion of the beam imaged to the DMD.
3. The device of claim 1 , further comprising an imaging unit, configured to record and/or monitor beam modes obtained from the output beam of the DMD.
4. The device of claim 3 , wherein the imaging unit comprises:
a filter, configured to filter the output beam from the DMD; and
a CCD camera, configured to record and/or monitor laser beam modes obtained from the filtered beam.
5. The device of claim 1 , wherein the micromirrors of the DMD are programmable to generate variable patterns to shape beams into arbitrary profiles.
6. The device of claim 1 , wherein the dispersion compensation unit is arranged so that the designated angular dispersion is positive if the angular dispersion introduced by the DMD is negative and the designated angular dispersion is negative if the angular dispersion introduced by the DMD is positive.
7. A laser scanning microscope comprising the device of claim 3 .
8. The microscope according to claim 7 , wherein the device is used in the microscope for controlling pulsed laser beam modes and z-scanning.
9. The microscope according to claim 7 , wherein the microscope is configured to control the beam modes and x-, y- and z-scanning, realizing random-access scanning.
10. The microscope according to claim 7 , wherein the microscope is a wide field, point-scanning, or line-scanning microscope based on pulsed lasers.
11. The microscope according to claim 7 , wherein the microscope is a super-resolution microscope based on pulsed lasers.