Thin-film large-area coherent light source, filter and amplifier apparatus and method

A passive spatial electromagnetic radiation filter apparatus comprising:

• a feedback structure having a top portion and a bottom portion of a thickness T and having an average refractive index N, said feedback structure being configured to produce a photonic mode of a predetermined frequency, said photonic mode being separated from a nearest lower frequency photonic mode by a frequency greater than determined in accordance with a following expression:
• c/2TN, wherein c is the speed of light in a vacuum;
• and
• a source for emitting electromagnetic radiation at said predetermined frequency within a cone that is generally perpendicular to said feedback structure through said feedback structure, wherein said feedback structure only transmits electromagnetic radiation of said predetermined frequency and having a wave vector substantially normal thereto, such that said electromagnetic radiation is passively spatially filtered as it passes through said feedback structure.

An electromagnetic radiation amplifier apparatus comprising:

• a feedback structure having a top portion and a bottom portion of a thickness T and having an average refractive index N, said feedback structure being configured to produce a photonic mode of a predetermined frequency, said photonic mode being separated from a nearest, to said predetermined frequency, lower frequency photonic mode by a frequency greater than determined in accordance with a following expression:
• c/2TN, wherein c is the speed of light in a vacuum;
• a light-amplifying medium disposed within said feedback structure and being configured to amplify electromagnetic radiation at said predetermined frequency;
• an electromagnetic radiation source for emitting electromagnetic radiation at said predetermined frequency perpendicular to said feedback structure through said first surface of said feedback structure into said structure, such that a beam emerges through said second surface, wherein said feedback structure only transmits electromagnetic radiation of said predetermined frequency having a wave vector substantially normal thereto;
• and
• variable excitation means, connected to said feedback structure, for applying gain of a selected magnitude to said feedback structure to thereby externally control a coherence area of said emerging beam, wherein said gain:
• a) ranges from a lower gain to a higher gain,
• b) is below a lasing threshold, and
• c) is sufficient to provide amplification for said emitted electromagnetic radiation at said predetermined frequency such that when said gain is changed between said lower gain and said higher gain, said electromagnetic radiation emitted from said second surface is amplified and changed in coherence area corresponding to said change in said gain.

A method for producing single mode large-area coherent lasing, comprising the steps of:

• a) providing a feedback structure of a thickness T and of an average refractive index N, having a top surface and a bottom surface, said feedback structure having refractive index variation, between said top and said bottom surfaces in accordance with a predefined profile;
• b) configuring said feedback structure by selecting said predefined profile such that said structure produces a photonic mode having a lasing threshold and being of a predetermined frequency, and a plurality of additional photonic modes of different frequencies, wherein said predefined profile is selected such that said predetermined frequency is greater than a value determined by a following expression:
• FL+c/2TN,
• wherein FL is a frequency of a nearest, to said predetermined frequency, lower frequency photonic mode of said plural additional photonic modes, and c is the speed of light in a vacuum;
• c) providing a light-emitting medium disposed within said feedback structure, said light-emitting medium being configured to produce optical gain when subjected to excitation;
• and
• d) exciting said light-emitting medium to produce said optical gain of a predetermined gain magnitude in said feedback structure, said predetermined gain magnitude being sufficient to at least meet said lasing threshold, such that coherent wide-area laser emission occurs at said predetermined frequency perpendicular to at least one of said top and bottom surfaces, wherein said wide-area laser emission remains coherent when said predetermined gain magnitude is selectively increased above said lasing threshold.

A method for passively spatially filtering electromagnetic radiation utilizing a feedback structure, comprising the steps of:

• a) providing a feedback structure of a thickness T and of an average refractive index N, having a top surface and a bottom surface, said feedback structure having refractive index variation, between said top and said bottom surfaces in accordance with a predefined profile;
• b) configuring said feedback structure by selecting said predefined profile such that said structure produces a photonic mode having a lasing threshold and being of a predetermined frequency, and a plurality of additional photonic modes of different frequencies, wherein said predefined profile is selected such that said predetermined frequency is greater than a value determined by a following expression:
• FL+c/2TN,
• wherein FL is a frequency of a nearest, to said predetermined frequency, lower frequency photonic mode of said plural additional photonic modes, and c is the speed of light in a vacuum;
• and
• c) emitting electromagnetic radiation, from an electromagnetic radiation source, at said predetermined frequency within a cone that is generally perpendicular to said feedback structure through said feedback structure, wherein said feedback structure only transmits electromagnetic radiation of said predetermined frequency and having a wave vector substantially normal thereto, such that said electromagnetic radiation is passively spatially filtered as it passes through said feedback structure.

A method for amplifying electromagnetic radiation utilizing a feedback structure comprising the steps of:

• a) providing a feedback structure of a thickness T and of an average refractive index N, having a top surface and a bottom surface, said feedback structure having refractive index variation, between said top and said bottom surfaces in accordance with a predefined profile;
• b) configuring said feedback structure by selecting said predefined profile such that said structure produces a photonic mode having a lasing threshold and being of a predetermined frequency, and a plurality of additional photonic modes of different frequencies, wherein said predefined profile is selected such that said predetermined frequency is greater than a value determined by a following expression:
• FL+c/2TN,
• wherein FL is a frequency of a nearest, to said predetermined frequency, lower frequency photonic mode of said plural additional photonic modes, and c is the speed of light in a vacuum;
• and
• c) providing a light-amplifying medium disposed within said feedback structure and being configured to amplify electromagnetic radiation at said predetermined frequency;
• d) emitting electromagnetic radiation, from an electromagnetic radiation source, at said predetermined frequency perpendicular to said feedback structure through said first surface of said feedback structure into said structure, such that a beam emerges through said second surface, wherein said feedback structure only transmits electromagnetic radiation of said predetermined frequency having a wave vector substantially normal thereto;
• and
• e) applying gain of a selective magnitude to said feedback structure, from a variable excitation device, to thereby externally control a coherence area of said emerging beam, wherein said gain:
• 1) ranges from a lower gain to a higher gain,
• 2) is below a lasing threshold, and
• 3) is sufficient to provide amplification for said emitted electromagnetic radiation at said predetermined frequency such that when said gain is selectively changed between said lower gain and said higher gain, said electromagnetic radiation emitted from said second surface is amplified and changed in coherence area corresponding to said change in said gain.