Leland Stanford Junior University

Guang-Yu Yin

Stephen E Harris

Andrew J Merriam

Maneesh Jain

Chih-Sung Chuu

Hui Xia

Scott J Sharpe

Improved production of entangled photon pairs (biphotons) via spontaneous parametric down conversion (SPDC) is provided. In one aspect, forward-wave SPDC is performed in a monolithic resonator (resonant for both signal and idler) having a double pass pump geometry to provide a spectrally bright source of biphotons. In another aspect, backward-wave SPDC is performed in a resonator (resonant for both signal and idler) to provide a spectrally bright source of biphotons. For either of these approaches, the biphotons can be made to have polarization entanglement by using quasi phasematching (QPM) with two QPM periods simultaneously.

Ultrabright long biphoton generation with non-linear optical material

A self-seeding laser comprises a slave oscillator cavity coupled to a Littman cavity that operates in a single longitudinal mode. The slave oscillator cavity comprises the following elements positioned in sequential order to provide a first beam path: an end mirror, a gain medium, a grating having a groove spacing, and an output mirror. The first beam path has an angle of incidence upon the grating, and light traveling along the first beam path is zeroth-order diffracted by the grating. A tuning mirror faces the grating, for reflecting light diffracted away from the first beam path by the grating. The tuning mirror establishes the Littman cavity. The gain medium is pumped by a pulsed pump beam. The pump beam activates a pump region within the gain medium, the pump region having a radius. The Littman cavity operates in the single longitudinal mode because the angle of incidence, the groove spacing, and the radius are adjusted so that an adjacent mode walk-off time of the Littman cavity is less than a mode build-up time of the Littman cavity. A gain in the Littman cavity is initially greater than a gain in the slave oscillator cavity; the laser is thereby self-seeded in the single longitudinal mode.

Method and apparatus for single longitudinal mode operation of pulsed laser oscillators using efficient self-seeding

A method for producing electromagnetically induced transparency (EIT) in atoms with hyperfine structure. EIT is the phenomenon in which a material (e.g. lead vapor) becomes transparent to a first electromagnetic frequency (a probe beam) when exposed to a second electromagnetic frequency (a coupling beam). In the present invention, the atom has hyperfine split energy levels. In the method of the present invention, the coupling and probe beams are tuned to transitions between the centers of gravity (COGs) of the hyperfine split levels. This allows high transparencies to be achieved in high opacity materials. Also, the present method can produce EIT in isotopically mixed materials. This is because the COGs of hyperfine split levels (in nuclear spin.notident.0 atoms) are generally coincident with nonhyperfine split levels (in nuclear spin=0 atoms). The method of the present invention is directly applicable to nonlinear sum and difference frequency generation.

Method for producing electromagnetically induced transparency in atoms

Efficient nonlinear processes in a nonlinear optical medium are achieved by combining the concept of electromagnetically induced transparency (EIT) and a strongly-driven atomic local oscillator. The present method uses a nonlinear optical medium having elementary entities, such as atoms or molecules, in which a ground state .vertline.1&gt; and a second state .vertline.2&gt; are selected such that the transition between the ground state .vertline.1&gt; and the second state .vertline.2&gt; is a dipole forbidden transition. An upper state .vertline.3&gt; selected from among the energy states .vertline.i&gt; above the ground state .vertline.1&gt; such that a two-photon transition between the ground state .vertline.1&gt; and the second state .vertline.2&gt; via the upper state .vertline.3&gt; is allowed. A strongly-driven coherent superposition state which gives rise to the strongly-driven local oscillator is produced by applying two pumping beams, P1 and P2, at frequencies corresponding to transitions between states .vertline.2&gt; and .vertline.3&gt; and between states .vertline.1&gt; and .vertline.3&gt;. The nonlinear optical medium prepared in this way is used for efficient sum-and-difference and parametric generation in .LAMBDA. and ladder systems.

Growing community of inventors

Mountain View, CA, United States of America

Guang-Yu Yin