Light generating apparatus and method

An optical system comprising:

• an input non-linear optical medium positioned across an input axis and configured to transform a portion of light, carried by first chirped pulses of light at a first nominal wavelength that have been received by the input non-linear optical medium, into second chirped pulses of light at a second nominal wavelength,
• a pulse compressor system including at least one pulse compressor that is configured to receive one of the first chirped and second chirped pulses of light but not the other of said first chirped and second chirped pulses of light and to over-compress said one of the first chirped and second chirped pulses of light to form, at an output of the pulse compressor system, over-compressed chirped pulses of light that have a chirp direction opposite to that of the first chirped pulses of light;
• a first optical sub-system configured to spatially overlap a beam carrying the over-compressed chirped pulses of light with (a) a beam carrying the other of said first chirped and second chirped pulses of light and with (b) an output axis at multiple points of the output axis;
• and
• a second optical sub-system configured to synchronize a time of arrival of the over-compressed pulses of light and a time of arrival of the other of said first chirped and second chirped pulses of light at a chosen location, the chosen location being at the output axis.