A degenerate four-wave mixing (DFWM) squeezed light apparatus includes one or more pump beams, a probe beam, a vapor cell, a repump beam, and a detector. The one or more pump beams includes an input power of no greater than about 150 mW. The vapor cell includes an atomic vapor configured to interact with overlapped pump and probe beams to generate an amplified probe beam and a conjugate beam. The repump beam is configured to optically pump the atomic vapor to a ground state and decrease atomic decoherence of the atomic vapor. The detector is configured to measure squeezing due to quantum correlations between the amplified probe beam and the conjugate beam. The one or more pump beams, the probe beam, and the repump beam are configured to generate two-mode squeezed light by DFWM with squeezing of at least 3 dB below shot noise.

A photonic integrated circuit (PIC) includes a first microresonator that generates a two-mode squeezed vacuum using spontaneous four-wave mixing. Specifically, the first microresonator uses a nonlinear optical medium to convert two pump photons into a pair of entangled signal and idler photons. Due to imperfect conversion efficiency, some of the pump light may co-propagate with the signal light and idler light. To remove this “unconverted” pump light, the PIC includes a second microresonator that is tuned to resonate with only the pump light. The second microresonator is located after the first microresonator and couples the unconverted pump light into a waveguide that guide the light off the PIC. Thus, the second microresonator acts as a notch filter. Integrating this pump filter onto the PIC adds negligibly to the path length of the squeezed light, and therefore saves the propagation losses incurred when using a much larger off-chip filter.

A device for the generation of ultrashort pulses, wherein an oscillator is formed by: a first and a second non-overlapping transmission band-pass filter, which can serve as reflecting end element of the oscillator; optically transparent means with non-linear Kerr coefficient χ.sup.(3) different from zero configured to achieve a spectral broadening by self-phase modulation of the signal transiting through these means; an optical waveguide that produces a positive gain; a node configured to receive a trigger signal designed to activate the operation of the oscillator; a trigger signal generating device comprising: a laser source, for example a microchip, configured to generate a laser pulse, preferably with a minimum bandwidth, having a duration of hundreds of ps, up to the ns; a coupling system designed to introduce the pulse of the trigger laser into a waveguide made of an optically transparent material characterised by a non-linear Kerr coefficient χ.sup.(3) different from zero, which is configured to produce two distinct effects in order to spectrally broaden the pulse of the trigger laser, and precisely: a) self-phase modulation four-wave mixing; the output of the waveguide supplies the trigger signal to the node. The pulses produced by the oscillator typically have a duration of the order of the picosecond and are easily reduced to the Fourier limit of circa 100 femtoseconds by means of a dispersive device.

Techniques disclosed herein relate to photon sources with high spectral purity and high brightness. In one embodiment, a photon-pair source includes a pump waveguide, a first resonator coupled to the pump waveguide to couple pump photons from the pump waveguide into the first resonator, a second resonator coupled to the first resonator, and an output waveguide coupled to the second resonator. The second resonator is configured to convert the pump photons into photon pairs. The second resonator and the first resonator are configured to cause a coupling-induced resonance splitting in the second resonator or the first resonator. The second resonator and the output waveguide are configured to couple the photon pairs from the second resonator into the output waveguide. In some embodiments, the photo-pair source includes one or more tuners for tuning at least one of the first resonator or the second resonator.

Kerr and electro-optic frequency comb generation in integrated lithium niobate devices is provided. In various embodiments, a microring resonator comprising lithium niobate is disposed on a thermal oxide substrate. The microring resonator has inner and outer edges. Electrodes are positioned along the inner and outer edges of the microring resonator. The electrodes are adapted to modulate the refractive index of the microring. A pump laser is optically coupled to the microring resonator. The microring resonator is adapted to emit an electro-optical frequency comb when receiving a pump mode from the pump laser and when the electrodes are driven at a frequency equal to a free-spectral-range of the microring resonator.

Embodiments of an optical signal copier and an optical parametric amplifier are disclosed herein, which are applied to the communications field. In the embodiments, the optical signal copier is included in the optical parametric amplifier, which generates an invalid signal in a process of transmitting signal light and pump light. The optical signal copier may separate the signal light from the invalid signal and then transmit the signal light to a signal processing module. In this way, the signal processing module may directly process the signal light that does not include the invalid signal, the invalid signal does not occupy transmission bandwidth of the optical parametric amplifier, and the effective transmission bandwidth of the optical parametric amplifier is relatively large.

A technology is described for a Photonic Integrated Circuit (PIC) radio frequency (RF) oscillator. The PIC RF oscillator can comprise an optical gain media coupled to a first mirror and configured to be coupled to the PIC. The PIC can comprise a first optical cavity located within the PIC, a tunable mirror to form a first optical path between the first mirror in the gain media and the first tunable mirror, and a frequency tunable intra-cavity dual tone resonator positioned within the first optical cavity to constrain the first optical cavity having a common optical path to produce tow primary laser tones with a tunable frequency spacing. A photo detector is optically coupled to the PIC and configured to mix the two primary laser tones to form an RF output signal with a frequency selected by the tunable frequency spacing of the two primary tones.

An entanglement-enhanced interferometry system includes a source of correlated photons configured to two-mode squeezed vacuum (TMSV), a polarizing splitter or off-axis polarizing coupler configured to separate the correlated photons into two paths, a polarization control device configured to rotate polarization of photons on one of the two paths relative to the photons on the other of the two paths in order to make photons indistinguishable, a coupler configured to entangle the indistinguishable photons, and a polarization maintaining fiber-based interferometer configured to use the entangled photons as the input state. The source of correlated photons might be a nonlinear element such as a periodically poled element such as a lithium niobate bulk crystal or waveguide. The interferometer might be a Mach-Zehnder or a common path configuration. The coupler might be a 50:50 coupler or a polarizing coupler 45 degrees off-axis.

Kerr and electro-optic frequency comb generation in integrated lithium niobate devices is provided. In various embodiments, a microring resonator comprising lithium niobate is disposed on a thermal oxide substrate. The microring resonator has inner and outer edges. Electrodes are positioned along the inner and outer edges of the microring resonator. The electrodes are adapted to modulate the refractive index of the microring. A pump laser is optically coupled to the microring resonator. The microring resonator is adapted to emit an electro-optical frequency comb when receiving a pump mode from the pump laser and when the electrodes are driven at a frequency equal to a free-spectral-range of the microring resonator.

In some implementations, a monolithic optical fiber may comprise a tapered core having a first diameter at an input end and a second diameter at an output end. The tapered core may comprise a first tapered region at the input end, a second tapered region at the output end, and a central region having a constant diameter that is larger than the first diameter and the second diameter. The first tapered region expands monotonically from the first diameter to the constant diameter of the central region along a length of the first tapered region, and the second tapered region contracts monotonically from the constant diameter of the central region to the second diameter along a length of the second tapered region. The monolithic optical fiber may be used as a delivery fiber to deliver a laser beam from a fiber laser engine to a process head.