United Technologies Corporation

John A Benda

Aristotle Parasco

Gary E Palma

Paul R Blaszuk

David C Smith

Edward A Sziklas

Sallie S Townsend

Harold L Cohen

Paul R Blazsuk

James L Forgham

A method of optical fiber manufacture involves the writing of a grating on the fiber using a laser. A first laser beam is directed on a first locality of the fiber having a circumference. A second laser beam is then directed on a second locality circumferentially displaced from the first locality. The first laser beam may be the second laser beam. In this way, a grating is formed on the fiber. The fiber may have a core and a cladding layer. The fiber may also comprise two gratings to form an interferometer.

Long period fiber Bragg gratings written with alternate side IR laser illumination

The present invention is a method which customizes the penetration depth of a heat-fusible powder used in solid freeform fabrication process such as laser sintering. The penetration depth of the heat-fusible powder is customized by combining opaque and transparent powders at a ratio which ensures that the beam contacts a portion of powder beneath its surface, thereby promoting complete layer sintering as well as adherence to previously sintered layers.

Absorption tailored laser sintering

A temperature-controlled laser sintering system includes a laser beam 12 which is focussed onto a sintering bed 38 by a focussing mirror 26 and a set of scanning mirrors 32, 34. Thermal radiation 114 emitted from the sintering bed 38 are imaged to the scanning mirrors and to a dichroic beamsplitter 110 which reflects such radiation but passes the wavelength of the laser beam 12. The radiation 118 is focussed onto an optical detector 126 which provides a signal on a line 128 to a power control circuit 104. The power control circuit 104 controls a modulator 100 which modulates the power of the laser beam 112 so as to maintain the thermal radiation emission 114 (and thus the temperature at the sintering location) at a substantially constant level.

Apparatus for temperature controlled laser sintering

A multiple beam laser sintering device includes a sintering beam 64 having a focal point at a powder bed 68 and at least one defocussed laser beam 116 incident on a region near the focal point of the focussed beam 64. The sintering beam 64 raises the temperature of the powder 84 to the sintering temperature. The defocussed beam 116 raises the temperature of the material surrounding the sintering beam 64 to a level below the sintering temperature, thereby reducing the temperature gradient between the sintering location and the surrounding material. Thermal radiation may be measured from one or both beams and used to control the power of one or both beams and the power of one or both beams may be controlled to maintain the temperature at a desired level. Alternatively, a plurality of defocussed beams may be used to provide either a plurality of thermal gradient steps, or to control the temperature of each region around the sintering point independently.

Apparatus for multiple beam laser sintering

A temperature-controlled laser sintering system includes a laser beam 12 which is focussed onto a sintering bed 38 by a focussing mirror 26 and a set of scanning mirrors 32,34. Thermal radiation 114 emitted from the sintering bed 38 are imaged to the scanning mirrors and to a dichroic beamsplitter 110 which reflects such radiation but passes the wavelength of the laser beam 12. The radiation 118 is focussed onto an optical detector 126 which provides a signal on a line 128 to a power control circuit 104. The power control circuit 104 controls a modulator 100 which modulates the power of the laser beam 112 so as to maintain the thermal radiation emission 114 (and thus the temperature at the sintering location) at a substantially constant level.

Method for performing temperature-controlled laser sintering

Method for performing multiple beam laser sintering employing focussed

A coupled multiple output ring laser system having a plurality of ring lasers 100,200 that are coupled together, each ring laser having separate output beams 159,280 and separate suppressor mirrors 228,282, is provided with two optical trombones 250,252 mounted on a common phase shifter 268, which changes the optical path length to the suppressor mirror 228 in the laser 100 and changes the optical path length of the mutual coupling path between the laser 100 and the laser 200 in an equal and opposite direction, thereby changing the phase of the output beam 159 of the laser 100 with respect to the output beam of the laser 200, without changing the phase of the output beam 280 from the laser 200. The invention works for any number of lasers and works equally well with reverse-to-forward coupling or forward-to-reverse coupling schemes.

Output phase shifter for coupled multiple-output ring lasers

An unstable resonator system is controlled in polarization by the use of a compound resonator in which the parent resonator is coupled to a polarization control leg by an aperture that passes a small portion of the output beam into a polarization control element and returns a polarized feedback beam mode-matched to the adjoint mode of the parent resonator.

Circular and elliptical polarization of a high power laser by adjoint

An unstable laser resonator is controlled in polarization by the use of a control leg coupled to the parent resonator and having a polarization control element therein, so that control of a low power beam in said control leg serves to control the polarization of the parent resonator.

Linear polarization control of high power lasers

An unstable laser resonator is controlled in polarization by the use of a control leg coupled to the parent resonator and having a linear polarization control element therein, so that control of a low power beam in said control leg serves to control the polarization of the parent resonator.

A modelocked laser with an unstable resonator configuration is described. The laser relies on adjoint mode feedback with a modulator in the low power feedback beam path which is not part of the main resonator. The optical cavity length and the path length of the feedback beam are adjusted to provide a pulsed, modelocked output beam.

Modelocked high power laser having an adjoint feedback beam

An optically pulsed laser with an unstable resonator configuration is described with two feedback beams. The laser relies on adjoint mode feedback with a single modulator in the low power feedback beam path. The laser is characterized by a two coupled adjoint feedback beams each configured to pass through the modulator in one direction only, thereby doubling the output power potential of the laser.

Optically pulsed laser having coupled adjoint beams

A continuously pumped ring laser is pulsed by modulating a small portion of one of the circulating beams and feeding back the modulated radiation in the adjoint mode.

Pulsed ring lasers using adjoint coupling control

An unstable resonator, dc excited, is pulsed using an adjoint coupled beam of low power as the pulsing element. The resonator feedback consists of the self-feedback and the adjoint beam feedback. The self-feedback can be sufficient for self-oscillation and pulsed operation can be achieved by controlling the repetition rate and the magnitude of the adjoint beam power. Complete control and shut-off between pulses with complete freedom of repetition rate is achieved if the self-feedback is insufficient for laser oscillation. The invention was demonstrated on a 10 kilowatt average power CO.sub.2 laser with pulse control provided by with a 100 watt adjoint feedback beam.

Optically pulsed laser

An improved ring laser system having mutual coupling between two or more ring laser resonators employs a two-step coupling process, in which coupling power is coupled into the adjoint forward mode of an adjacent resonator, from which it diffractively couples to the forward mode. A portion of forward-mode power is coupled into the adjoint reverse mode from which it diffractively couples to the reverse mode within each resonator. A portion of this reverse mode power is used to coupled into other resonators. A complementary configuration employs forward-mode radiation as the coupling radiation.

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Amston, CT, United States of America

John A Benda