Apparatus for providing optical radiation

A method for providing optical radiation, which method comprises:

• providing an optical input, a coupler, a first semiconductor amplifier, a preamplifier, a power amplifier, an output fibre, and a resonant cavity that are configured in series;
• providing a non-linear crystal in the resonant cavity;
• amplifying input optical radiation received by the optical input by the first semiconductor amplifier, the preamplifier, and the power amplifier;
• outputting the optical radiation from the power amplifier to the resonant cavity via the output fibre;
• forming a ring laser by connecting the resonant cavity to the optical input;
• configuring a controller to cause the waveguide to operate in saturation thereby enabling a reduction of at least one of spectral noise, temporal noise, and non-linear wavelength conversion of the optical radiation;
• using a detector to detect for an absence of the input optical radiation;
• and
• reducing an optical gain of the first semiconductor amplifier in order to prevent the first semiconductor amplifier from lasing,
• wherein
• the first semiconductor amplifier comprises a waveguide having a low reflecting facet;
• the first semiconductor amplifier is in a double pass configuration such that the low reflecting facet is connected to both the optical input and the preamplifier via the coupler.

A method for preventing failure of a ring laser, which method comprises:

• providing an optical input, a coupler, a first semiconductor amplifier, a preamplifier, a power amplifier, an output fibre, and a resonant cavity that are configured in series;
• providing a non-linear crystal in the resonant cavity;
• forming the ring laser by connecting the resonant cavity to the optical input;
• amplifying input optical radiation received by the optical input by the first semiconductor amplifier, the preamplifier, and the power amplifier;
• outputting optical radiation from the power amplifier to the resonant cavity via the output fibre;
• configuring a controller to cause the waveguide to operate in saturation thereby enabling a reduction of at least one of spectral noise, temporal noise, and non-linear wavelength conversion of the optical radiation;
• causing the resonant cavity to provide optical feedback in the form of the input optical radiation;
• and
• configuring the first semiconductor amplifier to supply optical radiation to the preamplifier in the event that the optical feedback is lost in order to prevent failure of the power amplifier,
• wherein
• the first semiconductor amplifier comprises a waveguide having a low reflecting facet;
• and
• the first semiconductor amplifier is in a double pass configuration such that the low reflecting facet is connected to both the optical input and the preamplifier via the coupler.