Modulator mirror

• US 4,973,131 A
• Filed: 02/03/1989
• Issued: 11/27/1990
• Est. Priority Date: 02/03/1989
• Status: Expired due to Term

• Current Assignee: Mcdonnell Douglas Corporation (The Boeing Co.)
• Original Assignee: Mcdonnell Douglas Corporation (The Boeing Co.)
• Inventors: Carnes, Rex G.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US07/306,615
• Time in Patent Office: 662 Days
• Field of Search: 350/164, 350/166, 356/352
• US Class Current: 359/238
• CPC Class Codes: G02B 26/0816 by means of one or more reflecting elements
• CPC Class Codes: G02B 5/284 of etalon type comprising a resonant cavity other than a thin solid film, e.g. gas, air, solid plates etalons for fibre optic multiplexing G02B6/29358; etalons for spectral measurement G01J3/26

Abstract

This modulator mirror comprises at least two partially transparent reflector stacks bonded to two separate substrates held apart by spacers to create a parallel gap between the partially transparent reflector stacks wherein the gap has a reference spacing of an even number of quarter wavelengths of the light energy contained within the beam to be modulated. The modulation is accomplished by causing a physical displacement between the two substrates such that the gap spacing varies between the reference pass position of the even number of quarter wavelengths and a second reference no pass position of about ± one quarter wavelength. The physical motion may be accomplished by electrostatic, piezo-electric, magnetic or other means.

Claims

1. A modulator for an optical system utilizing a beam of light containing energy in a narrow range about a wavelength of interest, the modulator comprising:

a first interference filter having two sides comprising a plurality of alternating first and second layers, both layers having an individual optical thickness equal to a precisely controlled fraction of the wavelength of the beam, the first layer comprising a high index of refraction material, and the second layer comprising a low index of refraction material, the first side of the filter being attached to a first transparent substrate through which the beam first enters the modulator;

a second interference filter having two sides comprising a plurality of alternating first and second layers, both layers having an individual optical thickness equal to a precisely controlled fraction of the wavelength of the beam, the first layer comprising a high index of refraction material, and the second layer comprising a low index of refraction material, the first side of the filter being attached to a second transparent substrate through which the beam exits the modulator when a beam transmission maximum exists;

wherein the second sides of the two interference filters face each other and are separated by sufficient spacer pads of equal thickness to define a parallel gap which is maintained at a relative vacuum between the second sides; and

means to cause relative motion of about one quarter wavelength between the two filters referenced to a first spacing of the parallel gap of an even multiple of quarter wavelength at which the transmission of the beam out of the modulator will be at a maximum wherein the means to cause relative motion comprises a first conductive metallization mechanically connected to the first interference filter and a second conductive metallization mechanically connected to the second interference filter wherein each metallization is connected to the modulated voltage source whereby modulation is the voltage connected to each metallization will cause th relative motion between the filters due to the action of the electrostatic forces acting between the two metallizations.

2. A modulator for an optical system utilizing a beam of light containing energy in a narrow range about a wavelength of interest, the modulator comprising:

a first interference filter having two sides comprising a plurality of alternating first and second layers, both layers having an individual optical thickness equal to a precisely controlled fraction of the wavelength of the beam, the first layer comprising a high index of refraction material, and the second layer comprising a law index of refraction material, the first side of the filter being attached to a first transparent substrate through which the beam first enters the modulator;

a second interference filter having two sides comprising a plurality of alternating first and second layers, both layers having an individual optical thickness equal to a precisely controlled fraction of the wavelength of the beam, the first layer comprising a high index of refraction material, and the second layer comprising a law index of refraction material, the first side of the filter being attached to a second transparent substrate through which the beam exits the modulator when a beam transmission maximum exists;

wherein the second sides of the two interference filters face each other and are separated by sufficient spacer pads of equal thickness to define a parallel gap containing a fluid having a high ionization potential between the second sides; and

means to cause relative motion of about one quarter wavelength between the two filters referenced to a first spacing of the parallel gap of an even multiple of quarter wavelengths at which the transmission of the beam out of the modulator will be at a maximum wherein the means to cause relative motion comprises a first conductive metallization mechanically connected to the first interference filter and a second conductive metallization mechanically connected to the second interference filter wherein each metallization is connected to the modulated voltage source whereby modulation is the voltage connected to each metallization will cause the relative motion between the filters due to the action of the electrostatic forces acting between the two metallizations.

3. A modulator for an optical system utilizing a beam of light containing energy in a narrow range about a wavelength of interest, the modulator comprising:

a first interference filter having two sides comprising a plurality of alternating first and second layers, both layers having an individual optical thickness equal to a precisely controlled fraction of the wavelength of the beam, the first layer comprising a high index of refraction material, and the second layer comprising a law index of refraction material, the first side of the filter being attached to a first transparent substrate through which the beam first enters the modulator;

a second interference filter having two sides comprising a plurality of alternating first and second layers, both layers having an individual optical thickness equal to a precisely controlled fraction of the wavelength of the beam, the first layer comprising a high index of refraction material, and the second layer comprising a law index of refraction material, the first side of the filter being attached to a second transparent substrate through which the beam exits the modulator when a beam transmission maximum exists;

wherein the second sides of the two interference filters face each other and are separated by sufficient spacer pads of equal thickness to define a parallel gap containing a fluid which is selectively absorbing to wavelengths other than the wavelength of interest between the second sides; and

means to cause relative motion of about one quarter wavelength between the two filters referenced to a first spacing of the parallel gap of an even multiple of quarter wavelengths at which the transmission of the beam out of the modulator will be at a maximum wherein the means to cause relative motion comprises a first conductive metallization mechanically connected to the first interference filter and a second conductive metallization mechanically connected to the second interference filter wherein each metallization is connected to the modulated voltage source whereby modulation is the voltage connected to each metallization will cause the relative motion between the filters due to the action of the electrostatic forces acting between the two metallizations.