Transmission grating beam combiner

A cascaded transmission grating optical beam combiner, comprising:

• first and second optical elements, each comprising:
• a substrate and a transmission grating formed on a surface of the substrate, the transmission grating of the first optical element configured to diffract first and second input beams such that said first and second input beams are combined into a first combined output beam and the transmission grating of the second optical element configured to diffract third and fourth input beams such that said third and fourth input beams are combined into a second combined output beam;
• a third optical element comprising a substrate and a transmission grating formed on a surface of the substrate, said third optical element arranged with respect to said first and second optical elements to receive said first combined output beam and said second combined output beam, said transmission grating of the third optical element configured to diffract and combine the first combined output beam and the second combined output beam into a third next-level combined output beam,
• first and second prisms positioned in the path of the first and second input beams, respectively, to decrease the width of the first and second input beams incident on the first optical element;
• third and fourth prisms positioned in the path of the third and fourth input beams, respectively, to decrease the width of the third and fourth input beams incident on the second optical element;
• and
• fifth and sixth prisms positioned in the path of the first and second combined output beams, respectively, to decrease the width of the first and second combined output beams incident on the third optical element.

A method of combining optical beams, the method comprising:

• providing a first transmission grating, said first transmission grating comprising a surface grating having a first grating spacing;
• providing first and second input beams having different wavelengths incident on the first transmission grating at first and second angles, respectively;
• transmitting the first and second beams having different wavelengths through the first transmission grating;
• diffracting the first and second beams, said first grating spacing and said first and second angles being such that said first and second input beams having different wavelengths are incident into two different diffraction orders of the first transmission grating and the first and second diffracted beams having different wavelengths are directed towards the same direction, such that the first transmission grating outputs a first combined beam at an angle not equal to the first incident angle and not equal to the second incident angle;
• decreasing the width of the first combined beam from the first transmission grating;
• providing a second transmission grating, said second transmission grating comprising a surface grating having a second grating spacing;
• providing third and fourth input beams having different wavelengths incident on the second transmission grating at third and fourth angles, respectively;
• transmitting the third and fourth beams having different wavelengths through the second transmission grating;
• diffracting the third and fourth beams, said second grating spacing and said third and fourth angles being such that said third and fourth input beams having different wavelengths are incident into two different diffraction orders of the second transmission grating and the third and fourth diffracted beams having different wavelengths are directed towards the same direction, such that the second transmission grating outputs a second combined beam at an angle not equal to the third incident angle and not equal to the fourth incident angle;
• providing a third transmission grating, said third transmission grating comprising a surface grating having a third grating spacing;
• transmitting the first and second combined beams through the third transmission grating;
• and
• diffracting the first and second combined beams, said third grating spacing and said first and second combined beams having angles such that said first and second combined beams are incident into two different diffraction orders of the third transmission grating and the first and second combined beams are directed towards the same direction, such that the third transmission grating outputs a third combined beam at an angle not equal to the angle of the first and second combined beams.