Abstract: Apparatus for providing optical radiation (1), which apparatus comprises a laser diode (2), a pulse generator (9), and a modulator (5), wherein: the pulse generator (9) is configured to emit picosecond pulses; the modulator (5) is configured to emit nanosecond pulses; the laser diode (2) has a first terminal (6) and a second terminal (7); the pulse generator (9) is connected to the first terminal (6); and the modulator (5) is configured to bias the laser diode (2) below a lasing threshold (8) of the laser diode (2), and the apparatus being characterized in that: the modulator (5) is connected to the second terminal (7); the pulse generator (9) comprises a semiconductor junction (32) connected to a differentiator (4); the semiconductor junction (32) is such that electric current flowing through the semiconductor junction (32) can be turned off more quickly than it can be turned on; and the differentiator (4) is such that a step change that occurs when the electric current flowing through the semiconductor junc

Abstract: Apparatus for providing optical radiation (1), which apparatus comprises a laser diode (2), a pulse generator (9), and a modulator (5), wherein: the pulse generator (9) is configured to emit picosecond pulses; the modulator (5) is configured to emit nanosecond pulses; the laser diode (2) has a first terminal (6) and a second terminal (7); the pulse generator (9) is connected to the first terminal (6); and the modulator (5) is configured to bias the laser diode (2) below a lasing threshold (8) of the laser diode (2), and the apparatus being characterized in that: the modulator (5) is connected to the second terminal (7); the pulse generator (9) comprises a semiconductor junction (32) connected to a differentiator (4); the semiconductor junction (32) is such that electric current flowing through the semiconductor junction (32) can be turned off more quickly than it can be turned on; and the differentiator (4) is such that a step change that occurs when the electric current flowing through the semiconductor junc

Abstract: Random number generation apparatus (2) is described that comprises a threshold detector (4) and an electrical noise generator (6). The electrical noise generator (6) has at least two channels (8a-8d) and each channel is arranged to generate an electrical noise signal. The threshold detector (4), which may comprise a digital input-output (DIO) card, is arranged to periodically compare this electrical noise signal with a threshold and to provide a binary data output that indicates whether the threshold has been exceeded. Each channel of the electrical noise generator comprises at least two amplifiers (10a-10c) electrically connected in series that preferably provide a gain of 50,000 or more. Use of the random number generation apparatus (2) for quantum cryptography applications is also described.

Abstract: An electro-optic waveguide polarisation modulator (20) comprising a waveguide core (4) having first and second faces defining a waveguide core plane, a plurality of primary electrodes (22, 24) arranged at a first side of the waveguide core plane and out of said plane, and at least one secondary electrode (26) arranged at a second side of the waveguide core plane and out of said plane, wherein the electrodes (22, 24, 26) are adapted in use to provide an electric field having field components (13, 15) in two substantially perpendicular directions within the waveguide core (4) so as modulate the refractive index thereof such that electromagnetic radiation propagating through the core (4) is converted from a first polarisation state to a second polarisation state.

Abstract: Random number generation apparatus (2) is described that comprises a threshold detector (4) and an electrical noise generator (6). The electrical noise generator (6) has at least two channels (8a-8d) and each channel is arranged to generate an electrical noise signal. The threshold detector (4), which may comprise a digital input-output (DIO) card, is arranged to periodically compare this electrical noise signal with a threshold and to provide a binary data output that indicates whether the threshold has been exceeded. Each channel of the electrical noise generator comprises at least two amplifiers (10a-10c) electrically connected in series that preferably provide a gain of 50,000 or more. Use of the random number generation apparatus (2) for quantum cryptography applications is also described.