Nipi refractive index modulation apparatus and method

An optical refractive index modulator, comprising:

• a nipi structure comprising alternating n and p doped semiconductor layers,
• first and second contact means establishing ohmic contacts with the n and p layers, respectively, said first and second contact means comprising respective contact elements extending through the nipi structure transverse to the n and p layers, each element being formed from a material that establishes ohmic contacts with its respective nipi layers and blocking contacts with the other layers, said first contact element comprising a ring enclosing aligned pixel portions of the nipi layers, and said second contact element comprising a wire extending through the nipi layers within the ring, and
• means for applying first and second voltages to the first and second contact means, respectively, the differential between the two voltages modulating the refractive index of the nipi structure.

An optical spatial phase modulator, comprising:

• a nipi structure,
• means responsive to the spatial intensity pattern of an input optical beam for generating a corresponding spatial voltage pattern, and
• means for applying the spatial voltage pattern to the nipi structure to modulate the structure's spatial refractive index in accordance with the spatial voltage pattern, whereby the structure spatially phase modulates an applied readout beam in accordance with its spatial refractive index modulation.

An optical refractive index modulator, comprising:

• a nipi structure comprising alternating n and p doped semiconductor layers,
• means for dividing said nipi structure into a spatial array of pixel elements, and
• means for applying a spatial array of modulated voltage differentials across adjacent pairs of n and p doped layers in a pattern corresponding to said spatial array of pixel elements to spatially modulate the nipi structure's refractive index, and thereby spatially modulate the phase of an optical beam applied to the nipi structure.

A method of modulating an optical beam, comprising:

• transmitting the beam through a nipi structure having alternating n and p doped semiconductor layers,
• applying a spatial voltage modulation between the n and p doped layers in a pixel array pattern to spatially modulate the nipi structure's refractive index, according to said pixel array pattern and said spatially modulated refractive index.

A method of converting an optical spatial intensity modulation to an optical spatial phase modulation, comprising:

• converting the optical spatial intensity modulation to a spatial voltage modulation,
• applying the voltage modulation to a nipi structure to spatially modulate the refractive index thereof, and
• directing a readout beam through the nipi structure to receive a spatial phase modulation corresponding to the refractive index modulation.