GB2087136A - Laser apparatus - Google Patents

Abstract

Laser apparatus includes a plurality of optical elements 10-13 and 16-18, Figure 1, which together define a folded laser optical cavity. A laser active medium 14 and flashtube pumping source 15 are located within the cavity. The components of the laser are supported by a single mass of material 19, Figure 2, having the same thermal and mechanical characteristics as the optical elements. <IMAGE>

Description

SPECIFICATION Laser apparatus Laser apparatus takes a great many forms and is used for many purposes. It is frequently necessary to provide a compact laser, and this may be done by folding the optical cavity by using mirrors or prisms to divert the optical path between the end reflectors of the laser. The problem introduced by the use of folding prisms or mirrors is the effect of temperature changes, vibration or other effects on the alignment of the various optical elements making up the laser.

The support for these optical elements must therefore be such as to reduce or prevent misalignment between these elements.

It is an object of the invention to provide laser apparatus in which the possibility of mechanical misalignment is reduced.

According to the present invention there is provided laser apparatus which includes a plurality of optical elements together defining a laser optical cavity, a laser active medium and pumping means located within the optical cavity, and supporting means to which said components are secured and comprising a single mass of material having the same mechanical and thermal characteristics as the optical elements.

Preferably the supporting means is made from the same material as the optical elements.

The invention will now be described with reference to the accompanying drawings, in which Figure 1 is an isometric view showing the layout of the optical elements of the laser; Figure 2 is an isometric view of the assembled laser; Figure 3 is a similar view of the supporting means; and Figure 4 is a sectional view along the line X-X of Figure 3.

Referring now to Figure 1, the laser to be described is a double-fold laser having a solid active medium excited by a flash tube. Crossed porro prisms 10 and 11 act as the end reflectors of the optical cavity. Two folding prisms 12 and 13 fold the optical axis of the laser in two perpendicular planes, prism 12 effecting a vertical fold and prism 13 a horizontal fold as shown in the drawing. The laser rod 14 and flash tube 15 are located between porro prism 10 and folding prism 12. The laser radiation is circularly polarised by a quarter-wave plate 16 located adjacent to porro prism 11. Since the end reflectors are prisms, the output beam must be derived by some force of beam splitter. A beamsplitting polariser 17 diverts from the laser cavity that portion of the radiation having a particular plane of polarisation.A second beam-splitting polariser 18 reflects this output beam in a direction parallel to the main axis of the laser.

The laser described above is conventional, and each of the optical elements described has to be supported in the correct position and alignment.

Although the use of prisms as end and folding reflectors makes it unnecessary for the angular alignment of these elements to be exact, it is still necessary to prevent excessive movement.

The assembled laser shown in Figure 2 has the same optical elements carried on a single mounting which comprises a block of material having the same thermal and mechanical characteristics as the optical elements. Hence the mounting block 19 will be formed from, say, glass having the same co-efficient of expansion as the prisms 10, 11, 12 and 13. Also shown in Figure 2 is a filter 20 positioned between the laser rod 14 and the flash tube 15, and part of a reflecting enclosure 21 which normally surrounds the laser rod and flash tube. The shape of the block 19 is shown in Figure 3 and 4. In general terms the block is formed with polished surfaces where it is necessary to attached optical elements, such as the outer ends 22 and 23. To reduce absorption in the block, slots are cut in the areas through which the laser radiation passes, such as at 24, 25, 26 and 27.

Vee-shaped grooves 28 in the ends of the block support the laser rod and flash tube.

The block 19 may be machined from a solid block, or may be moulded to the required shape. The block may be lightened in weight by cutting slots or apertures in other places. Alternatively, if losses are not important, then the slots may be omitted altogether.

The prisms could be integral with the block, being machined or moulded when the block is formed.

It will be clear that the actual arrangement of the optical elements of the laser may be varied, leading to a different shape of block. However, the result is still a very compact and robust laser with very high optical stability.

1. Laser apparatus which includes a plurality of optical elements together defining a laser optical cavity, a laser active medium and pumping means located within the optical cavity, and supporting means to which said components are secured and comprising a single mass of material having the same mechanical and thermal characteristics as the optical elements.

2. Apparatus as claimed in Claim 1 in which the supporting means is made from the same material as the optical elements.

3. Apparatus as claimed in Claim 2 in which the optical elements are formed integrally with the supporting means.

4. Apparatus as claimed in any one of the preceding claims in which material is removed from the supporting means in areas through which laser radiation may pass.

5. Laser apparatus substantially as herein described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Laser apparatus Laser apparatus takes a great many forms and is used for many purposes. It is frequently necessary to provide a compact laser, and this may be done by folding the optical cavity by using mirrors or prisms to divert the optical path between the end reflectors of the laser. The problem introduced by the use of folding prisms or mirrors is the effect of temperature changes, vibration or other effects on the alignment of the various optical elements making up the laser. The support for these optical elements must therefore be such as to reduce or prevent misalignment between these elements. It is an object of the invention to provide laser apparatus in which the possibility of mechanical misalignment is reduced. According to the present invention there is provided laser apparatus which includes a plurality of optical elements together defining a laser optical cavity, a laser active medium and pumping means located within the optical cavity, and supporting means to which said components are secured and comprising a single mass of material having the same mechanical and thermal characteristics as the optical elements. Preferably the supporting means is made from the same material as the optical elements. The invention will now be described with reference to the accompanying drawings, in which Figure 1 is an isometric view showing the layout of the optical elements of the laser; Figure 2 is an isometric view of the assembled laser; Figure 3 is a similar view of the supporting means; and Figure 4 is a sectional view along the line X-X of Figure 3. Referring now to Figure 1, the laser to be described is a double-fold laser having a solid active medium excited by a flash tube. Crossed porro prisms 10 and 11 act as the end reflectors of the optical cavity. Two folding prisms 12 and 13 fold the optical axis of the laser in two perpendicular planes, prism 12 effecting a vertical fold and prism 13 a horizontal fold as shown in the drawing. The laser rod 14 and flash tube 15 are located between porro prism 10 and folding prism 12. The laser radiation is circularly polarised by a quarter-wave plate 16 located adjacent to porro prism 11. Since the end reflectors are prisms, the output beam must be derived by some force of beam splitter. A beamsplitting polariser 17 diverts from the laser cavity that portion of the radiation having a particular plane of polarisation.A second beam-splitting polariser 18 reflects this output beam in a direction parallel to the main axis of the laser. The laser described above is conventional, and each of the optical elements described has to be supported in the correct position and alignment. Although the use of prisms as end and folding reflectors makes it unnecessary for the angular alignment of these elements to be exact, it is still necessary to prevent excessive movement. The assembled laser shown in Figure 2 has the same optical elements carried on a single mounting which comprises a block of material having the same thermal and mechanical characteristics as the optical elements. Hence the mounting block 19 will be formed from, say, glass having the same co-efficient of expansion as the prisms 10, 11, 12 and 13. Also shown in Figure 2 is a filter 20 positioned between the laser rod 14 and the flash tube 15, and part of a reflecting enclosure 21 which normally surrounds the laser rod and flash tube. The shape of the block 19 is shown in Figure 3 and 4. In general terms the block is formed with polished surfaces where it is necessary to attached optical elements, such as the outer ends 22 and 23. To reduce absorption in the block, slots are cut in the areas through which the laser radiation passes, such as at 24, 25, 26 and 27. Vee-shaped grooves 28 in the ends of the block support the laser rod and flash tube. The block 19 may be machined from a solid block, or may be moulded to the required shape. The block may be lightened in weight by cutting slots or apertures in other places. Alternatively, if losses are not important, then the slots may be omitted altogether. The prisms could be integral with the block, being machined or moulded when the block is formed. It will be clear that the actual arrangement of the optical elements of the laser may be varied, leading to a different shape of block. However, the result is still a very compact and robust laser with very high optical stability. CLAIMS

1. Laser apparatus which includes a plurality of optical elements together defining a laser optical cavity, a laser active medium and pumping means located within the optical cavity, and supporting means to which said components are secured and comprising a single mass of material having the same mechanical and thermal characteristics as the optical elements.

2. Apparatus as claimed in Claim 1 in which the supporting means is made from the same material as the optical elements.

3. Apparatus as claimed in Claim 2 in which the optical elements are formed integrally with the supporting means.

4. Apparatus as claimed in any one of the preceding claims in which material is removed from the supporting means in areas through which laser radiation may pass.

5. Laser apparatus substantially as herein described with reference to the accompanying drawings.