Laser

Abstract

A laser is disclosed having a housing formed of a block of glass-ceramic. The block is machined (or otherwise formed) to define one or more channels that act as a waveguide in two dimensions for light within the laser resonator. The channels extend between cavities also formed within the block which retain optical components of the laser, e.g. one or more of the gain medium, cavity mirrors, intermediate reflectors etc. The positioning, shape and size of each cavity is bespoke for the optical component it holds in order that each optical component is retained in optical alignment rigidly against the sides of the cavity.

Claims

1. A laser comprising: a gain medium; resonator mirrors; a pump mechanism configured to energise the gain medium and a hollow waveguide; wherein the hollow waveguide is arranged between the gain medium and at least one of the resonator mirrors to guide light between the gain medium and at least one of the resonator mirrors, the laser including a single integral piece body that: defines one or more conduits that provide, at least in part, the hollow waveguide, and includes one or more cavities to retain the resonator mirrors; and wherein cross-sectional dimensions of the hollow waveguide are configured to select a beam that is predominantly at lowest order TEM.sub.00 mode, that extends substantially the entire distance between the gain medium and the at least one resonator mirrors.

2. A laser according to claim 1, wherein the single integral piece body defines multiple conduits configured to provide multiple waveguides that lie between the gain medium and the resonator mirrors, and the laser comprises: a reflector to direct light between the conduits.

3. A laser according to claim 1, wherein the body defines a further cavity that retains an optical component configured to manipulate light within a resonator of the laser.

4. A laser according to claim 3, wherein the cavity is shaped and sized to retain the optical component in optical alignment.

5. A laser according to claim 3, wherein the single integral piece body comprises: one or more cavities to retain one or more of the gain medium and reflector.

6. A laser according to claim 1, comprising: a Q switch, the Q switch being retained in a further cavity provided by the single integral piece body so that light travelling through the hollow waveguide provided in the body will be incident upon the hollow waveguide.

7. A laser according to claim 1, wherein the conduit, or a further conduit defined by the body, is configured to guide a laser light output from the laser.

8. An optical circuit comprising: a body having hollow conduits that provide waveguides configured for guiding light travelling about the optical circuit, wherein at least one or more of the hollow conduits, or further conduits, in the body are configured to provide the hollow waveguide for the laser of claim 1.

9. An optical circuit according to claim 8, wherein the body comprises: a monolith in which a channel configured to provide the conduits is formed.

10. A method of manufacturing a laser comprising: providing a first single integral piece body that defines at least part of each of: two cavities; and a conduit that extends between the cavities, the conduit, when the laser is in use, acting as a hollow waveguide for light between the cavities, wherein the hollow waveguide provides an optical path, with cross-sectional dimensions which preferentially select a beam with the lowest order mode, that extends substantially the entire distance between a gain medium and at least one resonator mirrors; and locating a first optical component of the laser in one of the two cavities and a further optical component of the laser in a second of the two cavities.

11. A method according to claim 10, comprising: manufacturing the first single integral piece body by at least one of a machining process or an additive manufacture process.

12. A method according to claim 10, comprising; bringing together the first single integral piece with a second single integral piece, the first and second integral pieces cooperating to define a conduit that acts as a waveguide which, when the laser is in use, confines laser light about two orthogonal planes on each side of the optical axis.

13. A method according to claim 12, wherein the second integral piece defines a side of at least one of the cavities.

14. A method according to claim 10, wherein at least one of the cavities is positioned and shaped to support and retain at least one of the optical components in optical alignment.

15. A method according to claim 14, wherein at least one of the optical components is retained directly against a wall of at least one of the cavities.

16. A method according to claim 11, comprising: locating a first mirror providing a first end of a resonator of the laser in one of the two cavities and locating a second mirror providing a second end of the resonator of the laser in a second of the two cavities.

17. A method of manufacturing an optical circuit comprising, in addition to the method of claim 10: locating a further optical component in a further cavity of the single integral piece which, when the circuit is in operation, manipulates light that has been outputted from the laser.

Description

(1) The invention will now be described with reference to the figures in which:

(2) FIG. 1 is a plan schematic view of a laser comprising a hollow waveguide shown without lid;

(3) FIG. 2 is a side schematic section view of the laser FIG. 1 shown with lid;

(4) FIG. 3 is an end schematic section view of the laser of FIG. 1 shown with lid looking along the optical axis;

(5) FIG. 4 is a perspective view of a second embodiment of laser with lid absent to show optical layout;

(6) FIG. 5 is a perspective view of the laser of FIG. 4 shown with lid on; and

(7) FIG. 6 is schematic of an optical circuit comprising multiple hollow waveguide lasers and a beam combiner the lasers and combiner circuitry being integrated into a single body.

(8) FIGS. 1 to 3 illustrate a laser 1, having a laser gain medium 2 arranged between a first end resonator mirror 3 and second end resonator mirror 4; the latter being partially reflective so as to provide an output from the laser's 1 resonator that is formed between the resonator mirrors 3, 4. The laser 1 further comprises a first hollow waveguide 5 that guides light between the gain medium 2 and the first end resonator mirror 3, a second hollow waveguide 6 that guides light from the gain medium 2 to the second end resonator mirror 4, and a third hollow waveguide 7 that guides light transmitted through the output mirror 4 to provide an output port of the laser 1. The laser gain medium 2 is energised by a pump mechanism 8.

(9) The laser 1 comprises a chassis 9 formed from a single integral solid piece (monobloc), e.g. of Macor or other suitable material. The monobloc is milled, e.g. using a CNC process, to define a hollow channel that provides three sides of the first, second and third waveguides 5, 6, 7, and recesses for retaining mirrors 3 and 4 and pump mechanism 8. A portion of the channel also acts to retain (seated in) the laser gain medium 2. The laser 1 comprises a lid 10 also formed as a monobloc arranged to lie against chassis 9 to close the channels providing the waveguides 5, 6, and 7 of square cross section (see FIG. 3) so as to enclose around the optical axis X-X of the light within the resonator.

(10) The lid 10 may be profiled to provide a channel and/or recesses that correspond with the channel and recesses of the chassis 9 to provide a portion of the channel.

(11) The channel may have other cross section shapes.

(12) The dimensions of the width and length of the channel are chosen such that the Fresnel number is commensurate with an output beam that is predominantly TEM.sub.00, i.e. the lowest mode which is a preferred beam characteristic for many applications.

(13) The recesses are preferably shaped, sized and positioned such that the optical components are retained rigidly (i.e. without play) in the desired optical alignment. Nevertheless, though less preferred, the recesses may be adapted to additionally hold alignment means to allow the optical component to be moved within the recess to allow the component to be aligned manually.

(14) The pump mechanism may be of any known form suitable for use with the gain medium chosen.

(15) FIG. 4 is a variant embodiment of hollow waveguide laser 10 shown without lid so that the optical layout is visible. The laser 10 comprises a laser gain crystal 12 arranged optically between a first end resonator mirror 13 and a second end resonator mirror 14; a pump mechanism 15 to energise the laser gain crystal 12; a first reflecting prism 16; a second prism 17, a first pair of matched wedged prisms (also known as Risley prisms) 18, a second pair of matched wedged prisms 19; a polarising beam splitter 20; a Q switch 21; a half wave plate or quarter plate 22, and a quarter wave plate 23.

(16) A hollow waveguide extends between each of the optical components above (except pump 15) to provide a meandering optical pathway that extends between the resonator mirrors 13 and 14.

(17) The laser 10 comprises a chassis 24 and lid 25 (see FIG. 5) each formed as a monobloc of glass-ceramic such as, for example, Macor™ (though materials other than glass ceramic may be used). The chassis 24 is milled to provide channels that define portions of the hollow waveguides and recesses in which the resonator mirrors 13, 14 prisms 16, 17, beam splitter 20, Q switch 21 and plates 23, 23 are seated and retained in optical alignment with the optical pathway. In this embodiment, the laser gain crystal 12 is positioned within a cut out provided in the chassis 24; however, it may instead be retained within a channel through the chassis 24. The chassis 24 also comprises a broad channel 26 that provides an output port of the laser 10 from the beam splitter 20.

(18) Light entering either the first or second prisms 16, 17 is reflected back and forth therebetween three times (though could be more or less) travelling through a separate hollow waveguide each time. The meandering optical path allows for containment of a long resonator length in a laser having a physically short footprint.

(19) The functions of the wedged prisms 18, 19, plates 22, 23, Q switch 21, beam splitter 20 are well known and so will not be described in further detail. It will be appreciated that each of these components are optional.

(20) Although not preferred, a portion of the optical pathway between the resonator mirrors may extend through free space; e.g. as a result of a gap between the gain medium and the hollow waveguide.

(21) As illustrated in FIG. 5 the lid 25 may be comprised with through holes through which optical components may extend. This is optional. In an alternative arrangement the lid may completely contain the components.

(22) FIG. 6 is a schematic of an optical circuit 30 that functions as a beam combiner. The circuit 30 comprises two hollow waveguide lasers 31, 32 both of which are formed on a chassis 33 provided by a single integral piece (e.g. monobloc). In addition to the channels and recesses used to provide the waveguides and hold the optical components of the hollow waveguide laser 31, 32, the chassis 33 defines further channels, which together with a lid (not shown), provide enclosed hollow waveguides 34, 35 that guide laser outputs (though may not be formed to suppress propagation of modes higher than TEM.sub.00) from the respective lasers 31, 32 to a beam combiner component 36. The combined output from the beam combiner 36 is contained within a hollow waveguide 37 (also provided by a channel formed in the chassis 33) on a single beam axis. The form of the beam combiner 36 will depend on whether the wavelengths of the outputs from the lasers 31, 32 are the same or different. Either way the form of the beam combiner is conventional to those skilled in the art. It will be appreciated that in a variant embodiment more than two lasers may be formed on the chassis 22.

(23) It will be appreciated that alternative optical circuits could be arranged to provide additional or alternative functions. For example an integrated optical circuit including an integrated laser could be used to provide the optical circuitry of a LIDAR system.

(24) The above embodiments illustrate linear resonators though the conduits of the body may equally be arranged to provide a ring resonator.

(25) Although less preferred, rather than block form the chassis could be plate like, the plate material having approximately equal thickness across is width and length and profiled to define the conduits and recesses such as to resemble in form, a vacuum moulded piece.