M Squared Lasers Limited

Solus Technologies Limited

Graeme Peter Alexander Malcolm

Gareth Thomas Maker

Craig James Hamilton

Simon Munro

Lukasz Kornaszewski

Stephen Webster

John Nicholls

Gordon Robertson

William Miller

A method and system for injection-locking multiple optical amplifiers is disclosed. A master laser is employed to generate a continuous-wave output field. Optical modulators then produce first and second seed optical fields from the continuous-wave output field. The first and second seed optical fields provide an input to injection lock one or more optical amplifiers, optionally at different operating frequencies. Since the first and second seed optical fields are generated from the continuous-wave output field then the output fields of the optical amplifiers exhibit a high phase-coherence with each other and with the continuous-wave output field. Employing the first and second optical fields reduces the requirement to induce large frequency shifts on a single optical field. Techniques for phase-locking the output of the injection-locked laser systems are also provided to further reduce phase noise within the systems.

Injection-locked laser system

A method and apparatus for mounting optical components is described. The apparatus is suitable for mounting multiple optical components and comprises a baseplate having opposing first and second surfaces. Recesses or apertures are formed within the baseplate and are located upon the first or second surfaces so as to define thermally activated optic mounting areas. Pillars are then located within the thermally activated optic mounting areas and these provide a means for attaching the optical component to the baseplate. The employment of the recesses or apertures act to significantly reduce the thermal conduction throughout the baseplate. As a result preferential heating can be provided to the one or more thermally activated optic mounting areas while maintaining the baseplate with a desired mechanical strength. The optical mounting apparatus exhibits a high thermal stability thus making the apparatus ideally suited for use within commercial optical system.

Method and apparatus for mounting optical components

An electro-optic modulator (EOM) for altering an optical path length of an optical field is described. The EOM comprises first and second Brewster-angle cut nonlinear crystals having a first and second optical axis. The optical axes are orientated relative to each other such that when an optical field propagates through the nonlinear crystals it experiences no overall deviation. The nonlinear crystals are also arranged to be opposite handed relative to the optical field. The EOM has the advantage that its optical losses are lower when compared with those EOMs known in the art. In addition, the EOM can be inserted into, or removed from, an optical system without any deviation being imparted onto the optical field. This reduces the levels of skill and effort required on the part of an operator. The described method and apparatus for mounting the nonlinear crystals also suppresses problematic piezo-electric resonances within the nonlinear crystals.

Electro-optic modulator

A method and apparatus for mounting optical components is described. The apparatus () is suitable for mounting multiple optical components () and comprises a baseplate () having opposing first () and second () surfaces. Recesses or apertures () are formed within the baseplate and are located upon the first or second surfaces so as to define thermally activated optic mounting areas. Pillars () are then located within the thermally activated optic mounting areas and these provide a means for attaching the optical component to the baseplate (). The employment of the recesses or apertures act to significantly reduce the thermal conduction throughout the baseplate. As a result preferential heating can be provided to the one or more thermally activated optic mounting areas while maintaining the baseplate with a desired mechanical strength. The optical mounting apparatus exhibits a high thermal stability thus making the apparatus ideally suited for use within commercial optical system.

A laser diode drive system for generating a drive current for a laser diode is described. The laser diode drive system comprises a first laser diode driver connected to the laser diode by a first cable to provide a drive current source for the laser diode. A second laser diode driver is then connected to the laser diode by a second cable to provide a low current sink for the laser diode. A feedback control loop is employed to provide a feedback signal for the second laser diode driver from to sample of an output field of the laser diode. The laser diode drive system exhibits low power consumption while being capable of creating sufficient feedback bandwidth to reduce the excess optical noise by at least an order of magnitude at 1 MHz compared with laser diode drive systems comprising just a first laser diode driver.

Laser diode drive system

A nonlinear crystal comprising a first end face and an opposing second end face is described. The first and second end faces are separated along an optical axis of the nonlinear crystal by a length in the range of 0.25 mm and 2 mm. Although the length of the nonlinear crystal results in a reduction in the nonlinear effects induced on an optical field propagating through the crystal it also provides for reduced deviation experienced by the generated optical field when the nonlinear crystal is rotated. Therefore, when the nonlinear crystals are incorporated within an enhancement cavity their reduced length allows for the deviation of the output field to be minimised by servo control electronics arranged to adjust a single cavity mirror. This significantly reduces the complexity, and thus expensive of the servo control electronics when compared to those employed with the prior art enhancement cavities.

Nonlinear crystal

A method and apparatus for passively synchronising the repetition rate of two or more mode-locked lasers is described. The method and apparatus involve forming a first synchronising optical field () by separating a portion of an output field of a first mode-locked laser () and thereafter redirecting this synchronising optical field to form a driving signal for a second mode-locked laser (). Employing these techniques results in systems with timing jitter of less than 1 fs. The method is independent of the wavelength and polarisation at which the mode-locked lasers operate and so is not limited to use with any particular type of mode-locked laser. Since the technique is passive it does not require the employment of electronics, variable time delay paths or additional non-linear optical crystals. Therefore, the method and apparatus are significantly less complex than those known in the art and are not power limited by additional non-linear optical processes. Part of the output () of the first mode-locked laser () is redirected via a beam splitter () and beam steering mirrors () and a half-wave plate () to a polariser () in the beam line of the second mode-locked laser (). The seeding and synchronising signal from the first mode-locked laser () may be perpendicularly polarized with respect to the polarization of the second mode-locked laser () and may have a different wavelength.

Method and apparatus for repetition rate synchronisation of mode-locked lasers

An optical frequency mixing module is described that comprises a nonlinear medium for frequency mixing the photons of one or more input optical fields to generate an output optical field; a nonlinear medium tuner for automatically phase matching the nonlinear medium to the one or more input optical fields to select the wavelength of the output optical field generated by the nonlinear medium; and a first direction correcting optic. The position of the first direction correcting optic relative to the nonlinear medium is dependent upon the selected wavelength of the output optical field and therefore ensures that the position and angle of propagation of this field remains constant and independent of its wavelength of. The optical frequency mixing modules therefore provides a means for automatically selecting the wavelength of the output field with no deviation being imparted onto the position or angle of propagation of the output field.

Optical frequency mixing module

A nonlinear crystal comprising a first curved face and an opposing second curved face is described. The first and second curved faces are arranged to provide the nonlinear crystal with rotational symmetry about at least one axis of the nonlinear crystal. The nonlinear crystal allows for frequency tuning of a generated optical field that is generated by propagating a fundamental optical field through the nonlinear crystal by rotation of the nonlinear crystal about an axis of rotation without any significant, or minimal, deviation being introduced to the generated optical field. These nonlinear crystals can therefore be incorporated into an external cavity frequency doubler or mixer without any need for the employment of optical compensation optics or servo control electronics to automatically realign the cavity mirrors.

A mode locking semiconductor disk laser (SDL) comprising a resonator terminated by first and second mirrors and folded by a third mirror is presented. The third mirror includes a semiconductor disk laser (SDL) suitable for generating a resonator field having a predetermined central wavelength &#x3bb;, while the second mirror includes an intensity saturable mirror suitable for mode locking the resonator field at the predetermined wavelength. The central wavelength of the reflectivity profile of the first and or second mirrors is shifted to a wavelength shorter than the central wavelength &#x3bb;to suppress gain at wavelengths longer than the central wavelength &#x3bb;. By mismatching the reflectivity profile of the first and or second mirrors to that of the desired output wavelength provides a stable mode locked laser with significantly reduced noise.

Mode-locking semiconductor disk laser (SDL)

An apparatus and a method monitor fluid loss from one or more casks during a maturation process. The apparatus comprises a multi-pass absorption cell arranged in fluid communication with one or more fluid conduits, a pump and a monitoring system. The pump and fluid conduits transport a fluid sample (e.g. vapor sample) from a perimeter of the one or more casks to the multi-pass absorption cell. The monitoring system detects and identifies fluid within the multi-pass absorption cell.

Maturation monitoring apparatus and methods

A self mode locking laser and corresponding method is described. The laser comprises a resonator () terminated by first () and second () mirrors and folded by a third mirror (). The third mirror comprises a reflector () surmounted by a multilayer semiconductor gain medium () that includes at least one quantum well layer and an optical Kerr lensing layer (). A perturbator is also included that provides a means to induce a perturbation on an intensity of one or more cavity modes of the resonator. The pertubator is employed to induce a small perturbation on the intensity of the cavity modes of the resonator which is sufficient for the optical Kerr lensing layer to induce mode locking on the output field. The second mirror () comprises an intensity saturable mirror that provides a means for reducing the pulse widths of the generated output field e.g. to around 100 fs. A diamond heat spreader () is attached to the top of the half VCSEL gain medium () for improved cooling as well as representing the Kerr medium. Further folding mirrors (-) may be inserted to adjust the degree of astigmatism to be compensated for by the Kerr effect used for mode-locking.

Self mode-locking semiconductor disk laser (SDL)

An optical amplifier is described. The optical amplifier () comprises a semiconductor disk gain medium () including at least one quantum well layer () and a pump field source () for generating an optical pump field () for the semiconductor disk gain medium. The optical amplifier acts to generate an output optical field () from an input optical field () received by the optical amplifier and arranged to be incident upon the semiconductor disk gain medium. Employing a semiconductor disk gain medium within the optical amplifier allows it to be optically pumped and thus provided for increased stability and beam quality of the output optical field while allowing for the design of optical amplifiers which can operate across a broad range of wavelengths. The optical amplifier may be employed with continuous wave or pulsed input optical fields.

Optical amplifier

A passively mode-locking laser and corresponding method is described. The laser comprises a resonator () terminated by first () and second () mirrors and folded by a third () and fourth () mirror. The third mirror comprises a reflector () surmounted by a multilayer semiconductor gain medium () including at least one quantum well layer while the second mirror () comprises an intensity saturable mirror. The resonator is configured to provide a cross sectional area of an intra cavity resonating field on the intensity saturable mirror that is greater than or equal to a cross sectional area of the intra cavity resonating field on the multilayer semiconductor gain medium. This arrangement provides a passively mode-locking laser that exhibits increased stability when compared to those systems known in the art.

Passively mode-locking semiconductor disk laser (SDL)

The present invention describes a self mode locking laser and a method for self mode locking a laser. The laser () comprises a resonator terminated by first () and second () mirrors and folded by a third mirror (). The third mirror comprises a single distributed Bragg reflector () upon which is mounted a multilayer semiconductor gain medium () and which includes at least one quantum well layer and an optical Kerr lensing layer (). Self mode locking may be achieved by configuring the laser resonator such that the lensing effect of the Kerr lensing layer acts to reduce an astigmatism deliberately introduced to the cavity mode. The self mode locking of the laser may be further enhanced by selecting the length of the resonator such that a round trip time of a cavity mode is matched with an upper-state lifetime of one or more semiconductor carriers located within the gain medium.

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Glasgow, United Kingdom

Graeme Peter Alexander Malcolm