JP2006039166A - Spatial phase modulator having elastic deforming part for inclination control - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To contrive miniaturization, stable performance and cost reduction of a spatial phase modulator for short pulse laser. <P>SOLUTION: This is the wide band spatial phase modulator which is provided with a plurality of parallel plates composed of an optically transmissive material, a holding means for arraying the parallel plates in a freely spatially movable state, and a tilting means for changing the inclination of the parallel plates. The comprising parallel plates are made up of an optically transmissive material having a transparent laser beam-transmitting material. As the tilting means for changing the inclination of the parallel plates, the parallel plates are supported by a member that tends to be more elastically deformable than a light transmitting optical path section, with the part in question elastically deformed by an actuator. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a spatial phase modulator having an improved elastic deformation portion.

  A special feature is the spatial phase modulator of laser light that can be used to generate short pulse laser light or to recompress the pulse width of short pulse laser light that has been extended during transmission and propagation through a substance. No. 2000-187167. The spatial phase modulator can precisely control dispersion compensation, can be used in a wide wavelength range, and can be used regardless of the intensity of a pulse of laser light.

  FIG. 1 shows the concept of compression of the pulse width of the short pulse laser light in the above-described prior art. The laser beam 2 emitted from the short pulse oscillator 1 is reflected by the reflecting mirror 3 installed at an angle of 45 degrees and enters the diffraction grating 5 as a beam 4. The short wavelength side of the spectrum constituting the short pulse of the incident light is a beam 7 and the long wavelength side is a wavelength 8 which is wavelength-dispersed and propagates through spatially different paths and enters the collimating reflector 6. The incident light is reflected and directed to the phase modulator 11 as a parallel beam 10, but the beams traveling in different spatial sections undergo respective phase modulation while passing through different phase modulation elements 13-19. Thereafter, the light is reflected by the reflecting mirror 12 and returned to the original direction.

  At this time, the beam is changed from the original direction by a minute angle in a direction perpendicular to the direction of angular dispersion of the diffraction grating 5. This reflected beam again passes through each element of the phase modulator, is collected by the reflecting mirror 6, and returns to the diffraction grating 5. The returning position is a position displaced in the direction perpendicular to the paper surface, where it becomes a parallel beam again, returned to the direction of the reflecting mirror 3 as a beam 20, passes through the side of the reflecting mirror 3 and becomes a beam 20. When the beam 20 is used for processing, the beam 20 is condensed by an optical system such as a lens 21 and irradiated onto a workpiece 24 or the like to achieve the purpose.

  FIG. 2 shows an AA cross section of the structure of the conventional phase modulator shown in FIG. A transparent parallel plate 34 is attached to a rotatable structure such as a ball bearing 32 on the base 31, and the parallel plate is rotationally driven by a bimorph or piezo linear actuator so that the passing beam 35 is subjected to predetermined phase modulation. It is a structure that rotates. In order to align a plurality of parallel plates in parallel with each other in the direction perpendicular to the laser optical axis direction as indicated by 13-19 in FIG. 1, a plurality of rotatable ball bearings are passed through the shaft, and phase modulation optics is passed through the bearings. A plurality of parallel flat plates made of a transparent material are attached in parallel. The parallel plate rotates around the axis.

  Since this parallel plate 13-19 has a structure in which the parallel plate rotates about the bearing axis so that it can be tilted independently with respect to the optical axis 35, the bearing is fixed with respect to the positioning accuracy of the parallel plate. Play around the axis becomes a problem. In other words, the angle of the parallel plate depends on the manufacturing accuracy of the bearing, and in order to obtain sufficient accuracy of the bearing operation, a highly accurate submicron manufacturing accuracy is required for the bearing and the mounting housing of the bearing.

When normal bearings are used, the parallelism of multiple parallel plates deteriorates when individual parallel plates are driven to rotate, and the actual parallel plate tilt angle with respect to the tilt angle control command varies, so the transmitted light space The spatial phase error appears as a position error of the parallel plate set with respect to the angle command value depending on the space in which the parallel phase modulation degree is installed in each parallel plate. This leads to insufficient short pulse compression due to imperfect spatial phase control when performing pulse width compression of short pulses. For this reason, there is a drawback in that sufficient pulse compression cannot be performed and the pulse width may be increased.
JP 2000-187167 A

  In order to solve the above-described problems of the prior art, the present invention provides a spatial phase modulator having a parallel plate precision drive structure that enables high-precision modulation of the phase modulation degree according to the space. An object is to provide a phase modulator.

  The present invention relates to a broadband space having a plurality of parallel flat plates made of an optically transmissive material, support means for aligning the parallel flat plates in a spatially movable state, and tilting means for changing the tilt of the parallel flat plates. In the optical phase modulator, the tilting means for changing the tilt of the parallel plate solves the above problem by a spatial phase modulator which includes an actuator.

  According to a preferred embodiment of the present invention, the parallel plate is attached to a member that is more easily elastically deformed than the light transmission optical path portion. According to another preferred embodiment, the member that is more easily elastically deformed than the light transmission optical path is made of the same material and integral with the light transmission optical path. Further, the member that is more easily elastically deformed than the light transmission optical path portion may have a portion that is the same material as the light transmission optical path portion and is thinner than the light transmission optical path portion.

  According to another preferred embodiment of the present invention, the present invention provides a plurality of parallel plates made of an optically transmissive material, support means for aligning the parallel plates in a spatially movable state, and parallel plates. In the wideband spatial light phase modulator having a tilting means for changing the tilt of the parallel plate, the tilting means for changing the tilt of the parallel plate has a stacked piezo element and a mechanism for converting the displacement into an expanding and tilting motion. The above-mentioned problem is solved by a vessel.

  Moreover, it is preferable that the said inclination means can set an angle separately for every parallel plate.

  With the above structure, the mechanical play of the movable part supporting the parallel plate can be eliminated, so that the inclination of the parallel plate according to the command of the tilt angle can be uniquely determined. A spatial phase modulator that can measure high accuracy was realized.

  According to the present invention, there is provided a broadband spatial optical phase having a plurality of parallel plates made of an optically transmissive material, support means for aligning the parallel plates in a spatially movable state, and tilting means for changing the tilt of the parallel plates. In the modulator, the optical transmission material is a transparent parallel plate, and the parallel plate causes an angle change by elastic deformation of at least the mounting member of the parallel plate as a tilting means for changing the tilt of the parallel plate. By changing the optical path length of the transmitted light beam and eliminating the mechanical play in the mounting movable part, the tilt angle direction of the light transmission surface due to the bearing rotation error of the parallel plate like the conventional bearing rotation structure The phase modulation error due to the tilt in the right-angle direction can be eliminated, and the accurate spatial phase modulation according to the tilt command signal becomes possible.

In a broadband spatial light phase modulator comprising a plurality of parallel plates made of an optically transmissive material, support means for aligning the parallel plates in a spatially movable state, and tilting means for changing the tilt of the parallel plates, The optically transparent material consists of a parallel flat plate transparent to the laser beam, and as a tilting means to change the tilt of the parallel flat plate, attach the light-transmitting parallel flat plate to a member that easily elastically deforms the transmission part of the parallel flat plate from the light transmitting optical path A spatial phase modulator using a plurality of parallel plates provided with an actuator that causes elastic deformation was obtained.
The invention described in the claims of the present invention will be described with reference to FIGS.

  A first embodiment of the present invention will be described with reference to FIG. A portion 44 of the transparent parallel plate 45 is processed to a thickness sufficiently smaller than the thickness of the parallel plate 45. Alternatively, another thin thin elastic deformation plate spring is provided on the parallel plate to form a joined body, and this thin portion is bonded and fixed to the base 31 with an adhesive or the like. Since the parallel plate 45 drives the end opposite to the fixed end 44 in the direction of the arrow 48, the other end of the bimorph piezo actuator 39 having one end fixed to the base 40 is used as a drive source. Drive in the direction of arrow 50. When the laser beam passes through a part of the parallel plate 45, the optical path length determined by the inclination angle of the parallel plate, the refractive index and the thickness of the parallel plate is subjected to phase modulation by the change of the inclination angle. This phase modulation amount depends on the relative phase modulation amount of other spatial portions, and the characteristics of the modulated beam 20 are affected. Therefore, since it is necessary to accurately control the phase difference below the wavelength with respect to the spectrum of the other space, the modulation amount needs to be controlled with high accuracy.

  In this embodiment, since the transparent parallel plate is partly made of a thin part, there is no mechanical play during driving, and a phase modulation amount corresponding to the driving signal of the bimorph piezo actuator can be obtained. An accurate modulator can be realized. In many cases, the modulator 11 has a larger number than the number of modulation elements 13-19 spatially used, and in this case as well, a useless space for mounting such as a ball bearing is not required. Thus, parallel plates can be arranged side by side, and the phase modulator can be downsized.

  Since the tilt angle required for phase modulation is sufficient within 2 degrees, there is no functional shortage even with the above structure. With such a configuration, the relative angle of the parallel plate with respect to the incident beam 47 is changed by driving by the bimorph piezo actuator, and the optical path length passing through the parallel plate 45 is changed by the inclination angle, thereby changing the phase of the incident beam. be able to.

  In addition, although the example where the part 44 formed thinner than the parallel flat plate is shown at one place, when creating the parallel flat plate, a plurality of thinly processed portions are provided and elastic deformation is shared by the thin multiple parts. You may let them. In addition, the use of a piezoelectric linear actuator or other electromagnetic actuator as the actuator can be selected in accordance with the actual design.

  A second embodiment of the present invention will be described with reference to FIG. A parallel plate 54 is bonded and fixed to a deformed body 53 having a parallelogram-shaped hollow cross section fixed to the base 31 with an adhesive or the like. The parallel flat plate 54 is changed in angle by the bimorph piezo-actuator 39 in the direction of the arrow 58 as it is inclined by the deformation of the deformable body 53. This deformation drive is performed by the parallel plate 54 being moved in the direction of the arrow 58 by the contact portion 38 ′ by the bimorph piezo actuator 39 to which the drive signal is applied. Since the parallelogram-shaped deformable body 51 is a deformation in which the inclination angle of the parallel plate is at most 2 degrees, the deformation in the elastic deformation region is sufficient. The parallel plate 54 can be controlled in tilt angle by driving with a bimorph piezo actuator or the like, and the incident beam 55 is subjected to phase modulation to become an outgoing beam 57.

  The embodiment shown in FIG. 5 has a structure using the deformation itself of the bimorph piezo actuator as the deformation driver. The bimorph piezo actuator 61 is fixed to the base 31 using an adhesive or the like at the interface 60, and the other end 62 fixes the parallel plate 63 with an adhesive. Thus, deformation is caused by applying a drive voltage of the bimorph piezo actuator, thereby tilting the parallel plate. This structure can control the inclination angle of the parallel plate with the deformation of the bimorph piezo actuator itself, so that the deformation error due to the mechanical play of mounting can be eliminated. For example, it is necessary to fix the base 31 and the parallel plate which are rigid bodies at a place deviated from the deformed portion in the longitudinal direction of the bimorph piezo actuator. As a result, the incident beam 64 undergoes phase modulation to become an outgoing beam 65.

  A fourth embodiment will be described with reference to FIG. The embodiment of the present invention has a structure in which a laminated piezo-actuator is used as a deformation driving body. The displacement of the laminated piezo-actuator is converted into a rotational motion by using a mechanism for expanding the displacement and converting it into a rotational motion using elastic deformation of metal. By applying a driving voltage to the laminated piezo actuator, the conversion mechanism is deformed, thereby tilting the parallel plate. In this structure, the deformation of the laminated piezo-actuator is converted into the inclination angle of the parallel plate with a single member, so that the deformation error and the mounting position error due to mechanical play such as attachment and adhesion of the quartz plate can be eliminated. As a result, the incident beam 64 undergoes phase modulation to become an outgoing beam 65.

  As an application example of the present invention, the force is dispersed by a diffraction grating or a prism by a pulse of a mode-locked pulse laser of a titanium sapphire laser, the optical phase of each wavelength region is changed, and the pulse waveform when compressed again is stretched. It can be used for compression. As a result, the short pulse waveform can be controlled, and the processing characteristics can be enhanced in applications such as laser processing.

Conventional pulse laser pulse waveform control device using phase modulator Configuration diagram of a phase modulator that uses ball bearings at the top of the AA cross section in FIG. Example drawing using the same material as the parallel plate for the displacement part of the inclination angle as the elastic deformation body Example drawing using a parallelogram deformable body as an elastic deformable body at an inclination angle displacement portion Diagram of an embodiment using a bimorph piezo actuator in the displacement part of the inclination angle as an elastic deformation body Diagram of an embodiment using a laminated piezo-actuator in the displacement part of the inclination angle as an elastic deformable body

Explanation of symbols

1 ... Laser oscillator,
3 ... 45 degree reflector,
5 ... Diffraction grating,
6 ... concave reflector for collimation,
11 ... Phase modulator,
12 ... Reflector,
13-19 ... Parallel plate for phase modulation,
21 ... Condensing lens,
24 ... Workpiece,
31 ... Base,
32 ... Bearing,
34, 54, 45, 63 ... Parallel plates,
39, 61 ... bimorph piezo actuator,
40 ... Base,

Claims (6)

Broadband spatial light phase modulator comprising a plurality of parallel plates made of an optically transmissive material, support means for aligning the parallel plates in a spatially movable state, and tilting means for changing the tilt of the parallel plates In
The tilting means for changing the tilt of the parallel plate is a spatial phase modulator having an actuator.   The spatial phase modulator according to claim 1, wherein the parallel plate is attached to a member that is more easily elastically deformed than the light transmission optical path portion.   The spatial phase modulator according to claim 2, wherein the member that is more easily elastically deformed than the light transmission optical path portion is made of the same material and is integral with the light transmission optical path portion.   The spatial phase modulator according to claim 3, wherein the member that is more easily elastically deformed than the light transmission optical path has a portion that is the same material as the light transmission optical path and is thinner than the light transmission optical path. Broadband spatial light phase modulator comprising a plurality of parallel plates made of an optically transmissive material, support means for aligning the parallel plates in a spatially movable state, and tilting means for changing the tilt of the parallel plates In
The tilting means for changing the tilt of the parallel flat plate is a spatial phase modulator having a laminated piezo element and a mechanism for converting the displacement into a magnifying and tilting motion.   The spatial phase modulator according to claim 1, wherein the tilting unit can individually set an angle for each parallel plate.

Images