The Provost Fellows and Scholars of the College of the Holy and Undivided Trinity of Queen Elizabeth, Near Dublin

Eblana Photonics Limited

James Christopher O'Gorman

Paul McEvoy

Pascal Landais

Frederick Paul Logue

John Hegarty

David McDonald

Liam Barry

John A Patchell

Stephen Anthony Lynch

Brian J Kelly

Herve Armel Francois Folliot

Brian Joseph Kelly

John Anthony Patchell

Disclosed is a laser () comprising a lasing cavity with a lasing medium and primary optical feedback means in the form of a facet () at either end of the cavity, the laser cavity defining a longitudinally extending optical path; and secondary optical feedback means formed by a plurality of refractive index perturbations () in the laser cavity, each perturbation defining two interfaces (); characterized in that, for at least one perturbation, only one of the two interfaces contributes to optical feedback along the optical path. The present invention relaxes the lithographic tolerances for making single longitudinal mode devices and improves performance characteristics.

Semiconductor laser and method of manufacture

A semiconductor photodetector () for detecting short duration laser light pulses of predetermined wavelength in a light signal () comprises a micro-resonator () of vertical Fabry-Perot construction having a Bragg mirror pair, namely, a front mirror () and a rear mirror () with an active region () located between the front and rear mirrors (). An N-type substrate () supports the rear mirror (). The light signal () is directed into the active region () through the front mirror () while a pump beam () is directed into the active region () at an end () thereof. The spacing between the front and rear mirrors () is such as to cause light of the predetermined wavelength to resonate between the mirrors (). The semiconductor material of the active region () is selected so that one photon from each of the light signal () and the pump beam () are required to transfer one electron from a valence band () of the active region () across a bandgap () to a conduction band () so that the active region operates on the principle of Two-Photon Absorption. On the active region () being simultaneously subjected to the pump beam and light of the predetermined wavelength in the light signal () electrons are transferred by Two-Photon Absorption from the valence band () to the conduction band (), thus causing a change in the voltage developed across the active region (). The change in voltage is detected between an electrode () on the substrate () and electrodes () on the front mirror () thereby indicating the presence of light of the predetermined wavelength in the light signal ().

Semiconductor photodetector

This invention generally relates to semiconductor devices, for example lasers and more particularly to single frequency lasers and is directed at overcoming problems associated with the manufacture of these devices. In particular, a laser device is provided formed on a substrate having a plurality of layers (), the laser device comprising at least one waveguide (for example a ridge) established by the selective removal of sections of at least one of the layers. Wherein alignment features are provided on the device to facilitate subsequent placement.

Method of manufacturing a semiconductor device with outline of cleave marking regions and alignment or registration features

A laser diode () having an optical path () defined in an active layer () which is sandwiched between a substrate layer () and a top layer () and defined by a ridge () formed in the top layer () outputs laser light of a single predetermined wavelength. Refractive index altering grooves () extending transversely in the top layer () are provided at spaced apart locations for altering the refractive index of the active layer () along the optical path at partial reflecting locations () for causing partial longitudinal reflections of the laser light generated in the optical path () so that standing waves or harmonics thereof of the single predetermined wavelength are set up between the respective partial reflecting locations () and a first mirror facet () in the optical path (). In order that the standing waves set up between the partial reflecting locations () and the first mirror facet () are harmonics of the predetermined single wavelength, the refractive index altering grooves () are located along the ridge () for forming the reflecting locations () at distances from the first mirror facet () which correspond to the effective length of the optical path () resulting from the affect of the inclusion of the reflecting locations () rather than at locations corresponding to the actual length of the light path ().

Optical waveguide and a method for providing an optical waveguide

A laser diode () for outputting light of a single mode comprises a substrate layer (), a cladding layer () and a compound light propagating layer () comprising first, second, third and fourth layers (to). A wave guiding region () of refractive index lower than its adjacent regions is defined by the third layer () by two quantum wells () positioned at the anti-node of light of a single mode which is propagating in the third layer () for propagating and amplifying the single mode light. A central ridge () locates the wave guiding region transversely of the direction of light propagation. The wave guiding region () can also be defined by shaping the top cladding layer () by forming an elongated central channel through the central ridge ().

Laser diode

A semiconductor self-pulsating laser diode ( ) comprises a wave guiding layer ( ) sandwiched between lower and upper cladding layers ( ). A current blocking layer ( ) defining a slot ( ) through which pumping current is directed through the laser diode between upper and lower contact plates ( ) defines an active wave guiding region ( ). The current blocking layer ( ) is shaped by the formation of longitudinally extending recesses ( ) for defining the active wave guiding region ( ) such that a central pulse light generating region ( ) is formed surrounded by an outer light propagating region ( ). As the laser diode is continuously pumped, an effective step change in refractive index between the wave guiding layer ( ) and the outer light propagating region ( ) is formed, and the carrier density and refractive index profiles across the active wave guiding region ( ) vary as each light pulse cycle progresses. Initially, the carrier density in the central pulse light generating region rises relative to the carrier density in the light propagating region until the difference between the refractive index of the pulse light generating region and the refractive index of the light propagating region is at its greatest, and the carrier density of the pulse light generating region reaches its lasing threshold value. At this stage lasing commences in the active wave guiding region . Lasing in the pulse light generating region progressively reduces the carrier density therein, which in turn progressively reduces the relative difference between the refractive index of the pulse light generating region and the light propagating region until the refractive index of the pulse light generating region approaches the refractive index of the light propagating region , thereby increasing guiding of lasing light into the pulse light generating region for emission of the light pulse therefrom. At that stage the carrier density of the active wave guiding region falls below its lasing threshold value, thus extinguishing the lasing light, and the next light pulse cycle commences.

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Dublin, Ireland

James Christopher O'Gorman