Apparatus and method for adjusting the wavelength of light

An imaging device, display or projection device comprising an optical arrangement for adjusting the wavelength of light, the optical arrangement comprising:

• a first light source arranged to generate a first beam of light at a first wavelength;
• a second light source arranged to generate seed light at a second wavelength;
• a first Raman shifting medium arranged to receive the light from the first light source in combination with the seed light from the second light source, and to produce, by stimulated Raman scattering, output light at the second wavelength and having temporal properties determined by those of the first beam of light;
• a third light source arranged to generate seed light at a third wavelength;
• and
• a second Raman shifting medium arranged to receive the output light from the first Raman shifting medium in combination with the seed light from the third light source, and to produce, by stimulated Raman scattering, output light at the third wavelength and having temporal properties determined by those of the output light from the first Raman shifting medium;
• wherein the third wavelength is greater than the second wavelength, and the second wavelength is greater than the first wavelength;
• wherein the frequency difference between the first beam of light and the seed light from the second light source is a frequency difference where the first Raman shifting medium exhibits Raman gain;
• wherein the frequency difference between the output light from the first Raman shifting medium and the seed light from the third light source is a frequency difference where the second Raman shifting medium exhibits Raman gain;
• and
• wherein the second Raman shifting medium has a different composition from the first Raman shifting medium.

A method of adjusting the wavelength of light, comprising:

• generating, using a first light source, a first beam of light at a first wavelength;
• generating, using a second light source, seed light at a second wavelength;
• arranging a first Raman shifting medium to receive the light from the first light source in combination with the seed light from the second light source, and to produce, by stimulated Raman scattering, output light at the second wavelength and having temporal properties determined by those of the first beam of light;
• generating, using a third light source, seed light at a third wavelength;
• and
• arranging a second Raman shifting medium to receive the output light from the first Raman shifting medium in combination with the seed light from the third light source, and to produce, by stimulated Raman scattering, output light at the third wavelength and having temporal properties determined by those of the output light from the first Raman shifting medium;
• wherein the third wavelength is greater than the second wavelength, and the second wavelength is greater than the first wavelength;
• wherein the frequency difference between the first light and the seed light from the second light source is a frequency difference where the first Raman shifting medium exhibits Raman gain;
• wherein the frequency difference between the output light from the first Raman shifting medium and the seed light from the third light source is a frequency difference where the second Raman shifting medium exhibits Raman gain;
• and
• wherein the second Raman shifting medium has a different composition from the first Raman shifting medium.