Bookham Technology Limited

Oclaro Technology Limited

Berthold Schmidt

Susanne Pawlik

Achim Thies

Boris Sverdlov

Christoph S Harder

Silke Traut

Norbert Lichtenstein

Semiconductor laser diodes, particularly high power AlGaAs-based ridge-waveguide laser diodes, are often used in opto-electronics as so-called pump lasers for fiber amplifiers in optical communication lines. To provide the desired high power output and stability of such a laser diode and avoid degradation during use, the present invention concerns an improved design of such a device, the improvement in particular significantly minimizing or avoiding (front) end section degradation of such a laser diode and significantly increasing long-term stability. This is achieved by separating the waveguide ridge into an active main ridge section () and at least one separate section () located at an end of the laser diode, which may be passive. The separation is provided by a trench or gap () in the waveguide ridge. The active waveguide section () is at least partly covered by the electrode () providing the carriers that does not extend to cover the separate ridge section (), which thus remains essentially free of carriers injected through said electrode (). There may be a plurality such separate ridge sections, e.g. two separate ridge sections (), one at each end of the laser diode, dividing the ridge waveguide into three ridge sections, an active main ridge section () in the center and a passive separate ridge section () at either end. The trenches () between the sections and/or the shape and size of the separate ridge section (s) () may be adjusted to act as spatial mode filters.

High power semiconductor laser diode

Semiconductor laser diodes, particularly high power ridge waveguide laser diodes, are often used in opto-electronics as so-called pump laser diodes for fiber amplifiers in optical communication lines. To provide the desired high power output and stability of such a laser diode and avoid degradation during use, the present invention concerns an improved design of such a device, the improvement concerns a method of suppressing the undesired first and higher order modes of the laser which consume energy and do not contribute to the optical output of the laser, thus reducing it's efficiency. This novel effect is provided by a structure comprising CIG&#x2014;for Complex Index Guiding&#x2014;elements on top of the laser diode, said CIG being established by fabricating CIG elements consisting of one or a plurality of layers and containing at least one layer which provides the optical absorption of undesired modes of the lasing wavelength. This CIG preferably contains an insulating layer as a first contact layer to the semiconductor. The CIG elements are manufactured by a selected sequence of processing steps, in particular several masking steps, and are specifically shaped, both in thickness and coverage of the laser's semiconductor body, to provide desired suppression characteristics. Further, the CIG elements may be combined with the contact layer usually providing the electrical input power to the laser diode.

Semiconductor laser diodes, particularly high power AlGaAs-based ridge-waveguide laser diodes, are often used in opto-electronics as so-called pump laser diodes for fiber amplifiers in optical communication lines. To provide the desired high power output and stability of such a laser diode and avoid degradation during use, the present invention concerns an improved design of such a device, the improvement in particular significantly minimizing or avoiding (front) end section degradation of such a laser diode and significantly increasing long-term stability compared to prior art designs. This is achieved by establishing one or two 'unpumped end sections' of the laser diode. One preferred way of providing such an unpumped end section at one of the laser facets () is to insert an isolation layer () of predetermined position, size, and shape between the laser diode's semiconductor material and the usually existing metallization (). A further embodiment shows separate, further isolation layers () extending along the laser diode, potentially abutting the ridge waveguide of the laser.

Semiconductor laser diodes, particularly high power ridge waveguide laser diodes, are often used in opto-electronics as so-called pump laser diodes for fiber amplifiers in optical communication lines. To provide the desired high power output and stability of such a laser diode and avoid degradation during use, the present invention concerns an improved design of such a device, the improvement in particular consisting in a way of suppressing the undesired first and higher order modes of the laser which consume energy and do not contribute to the optical output of the laser, thus reducing it's efficiency. Essentially, the novel effect is provided by a structure comprising CIG&#x2014;for Complex Index Guiding&#x2014;elements on top of the laser diode. These CIG elements consist of one or a plurality of layers and must contain at least one layer which provides the optical absorption of undesired modes of the lasing wavelength and preferably contains an insulating layer as a first contact layer to the semiconductor. The CIG elements may be specifically shaped, both in thickness and coverage of the laser's semiconductor body, to provide desired suppression characteristics. Further, the CIG elements may be combined with the contact layer usually providing the electrical input power to the laser diode.

High power semiconductor laser diode and method for making such a diode

A pump laser diode for providing improved stability at various operating temperatures is disclosed. It includes a Fabry-Perot cavity formed by laser facets. Bragg Gratings or Fiber Bragg Gratings (FBG) in a pump module are provided, wherein the optical mirror losses are made to increase for wavelengths longer than the required emission wavelength, thus permitting the diode to be locked to an emission wavelength while operating at different temperatures. A stack of materials with different refractive indices is deposited on the back facet of the laser diode to achieve a change in optical mirror losses over longer wavelengths.

Pump laser diode with improved wavelength stability

Semiconductor laser diodes, particularly high power ridge waveguide laser diodes, are often used in opto-electronics as so-called pump laser diodes for fiber amplifiers in optical communication lines. To provide the desired high power output and stability of such a laser diode and avoid degradation during use, the present invention concerns an improved design of such a device, the improvement in particular consisting of novel design of the ridge waveguide of the laser. Essentially the novel design consists in a segmented ridge waveguide having at least two straight segments, i.e. segments with constant, but different cross sections or widths, and at least one flared segment connecting the two different straight segments. A further improvement can be achieved by combining this approach with a laser diode design termed &ldquo;unpumped end sections&rdquo; and described in copending U.S. patent application Ser. No. 09/852,994, entitled &ldquo;High Power Semiconductor Laser Diode&rdquo;. Preferable for an advantageous manufacturing process is a segmented ridge waveguide design with three straight segments, at least two of them differing in cross section or width, and two flared segments connecting the differing straight segments. This latter design results in a wafer pattern of identical and identically oriented laser diode structures, thus allowing the use of standard manufacturing processes.

Semiconductor laser diodes, particularly high power AlGaAs-based ridge-waveguide laser diodes, are often used in opto-electronics as so-called pump laser diodes for fiber amplifiers in optical communication lines. To provide the desired high power output and stability of such a laser diode and avoid degradation during use, the present invention concerns an improved design of such a device, the improvement in particular significantly minimizing or avoiding (front) end section degradation of such a laser diode and significantly increasing long-term stability compared to prior art designs. This is achieved by establishing one or two &ldquo;unpumped end sections&rdquo; of the laser diode. One preferred way of providing such an unpumped end section at one of the laser facets ( ) is to insert an isolation layer ( ) of predetermined position, size, and shape between the laser diode's semiconductor material and the usually existing metallization ( ).

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Erlenbach/Zurich, Switzerland

Berthold Schmidt