An optical semiconductor device includes an active layer having a plurality of quantum dot layers. The plurality of quantum dot layers include: a first quantum dot layer doped with a p-type impurity; and a second quantum dot layer doped with an n-type impurity and having an emission wavelength different from that of the first quantum dot layer.

A laser transmitter including a waveform controller arranged to generate a waveform script having at least one of a pulse repetition frequency setting, a pulse duration setting, and a pulse amplitude pre-warp setting. The transmitter also includes an optical waveform generator arranged to: i) receive the waveform script, ii) generate pre-warped signal pulses based on the waveform script to compensate for gain distortion effects of a laser power amplifier, and iii) output the pre-warped signal pulses. The laser power amplifier is arranged to: i) receive the pre-warped signal pulses, ii) receive a continuous wave signal, and iii) output amplified signal pulses that maintain a substantially constant drive intensity at the input of a non-linear wavelength converter. The non-linear wavelength converter is arranged to receive the amplified signal pulses and emit wavelength-converted pulses.

A laser transmitter including a waveform controller arranged to generate a waveform script having at least one of a pulse repetition frequency setting, a pulse duration setting, and a pulse amplitude pre-warp setting. The transmitter also includes an optical waveform generator arranged to: i) receive the waveform script, ii) generate pre-warped signal pulses based on the waveform script to compensate for gain distortion effects of a laser power amplifier, and iii) output the pre-warped signal pulses. The laser power amplifier is arranged to: i) receive the pre-warped signal pulses, ii) receive a continuous wave signal, and iii) output amplified signal pulses that maintain a substantially constant drive intensity at the input of a non-linear wavelength converter. The non-linear wavelength converter is arranged to receive the amplified signal pulses and emit wavelength-converted pulses.

The de-multiplexing unit 2 de-multiplexes an inputted optical wavelength multiplexed signal into a first optical wavelength multiplexed signal having a first wavelength band and a second optical wavelength multiplexed signal having a second wavelength band in a longer wavelength band than the first wavelength band. The first optical amplifier 3 amplifies the first optical wavelength multiplexed signal. The second optical amplifier 4 amplifies the second optical wavelength multiplexed signal. The multiplexer 5 multiplexes the amplified first optical wavelength multiplexed signal and the amplified second optical wavelength multiplexed signal and outputs the multiplexed signal to a Raman amplifier 6. The first optical amplifier 3 adjusts the amplification rate of the first optical wavelength multiplexed signal so that the intensity of light in the second wavelength band is compensated for by the Raman effect in the Raman amplifier 6.

Methods and systems are disclosed for using a chromatic lens system to provide a flying focusi.e., an advanced focusing scheme enabling spatiotemporal control of a focal location. In a method, a photon beam is emitted from a source at a wavelength. The photon beam may have more than one wavelength. The photon beam is focused to a focal location using a chromatic lens system. The focal location is at a first longitudinal distance along an optical axis from the chromatic lens system. The wavelength of the photon beam is changed as a function of time to change the focal location as a function of time. The wavelength may be changed such that the focal location changes with a focal velocity.

The de-multiplexing unit 2 de-multiplexes an inputted optical wavelength multiplexed signal into a first optical wavelength multiplexed signal having a first wavelength band and a second optical wavelength multiplexed signal having a second wavelength band in a longer wavelength band than the first wavelength band. The first optical amplifier 3 amplifies the first optical wavelength multiplexed signal. The second optical amplifier 4 amplifies the second optical wavelength multiplexed signal. The multiplexer 5 multiplexes the amplified first optical wavelength multiplexed signal and the amplified second optical wavelength multiplexed signal and outputs the multiplexed signal to a Raman amplifier 6. The first optical amplifier 3 adjusts the amplification rate of the first optical wavelength multiplexed signal so that the intensity of light in the second wavelength band is compensated for by the Raman effect in the Raman amplifier 6.

Methods and systems are disclosed for using a chromatic lens system to provide a flying focusi.e., an advanced focusing scheme enabling spatiotemporal control of a focal location. In a method, a photon beam is emitted from a source at a wavelength. The photon beam may have more than one wavelength. The photon beam is focused to a focal location using a chromatic lens system. The focal location is at a first longitudinal distance along an optical axis from the chromatic lens system. The wavelength of the photon beam is changed as a function of time to change the focal location as a function of time. The wavelength may be changed such that the focal location changes with a focal velocity.

Disclosed are a laser device which uses alexandrite crystal and is capable of suppressing abnormal oscillation even if the size thereof is reduced and suppressing damage to an AR coating on a Q switch or alexandrite crystal, and a photoacoustic measurement device. A laser rod 11 includes alexandrite crystal. A flash lamp 12 irradiates the laser rod 11 with excitation light. A resonator includes a pair of mirrors 14 and 15 with the laser rod 11 sandwiched therebetween. A Q switch 16 is inserted into the optical path of the resonator and controls the Q value of the resonator. A polarizer 17 is inserted into the resonator and is a non-coated Brewster polarizer which selectively transmits light in a predetermined polarization direction among light emitted from the laser rod.

A laser drive circuit compensates for laser diode dynamics. A compensation value is determined from a sum of weighted basis functions. The basis functions may be a function of current desired optical powers and/or past desired optical powers. The weights may be updated periodically based at least in part on accumulated basis function outputs and measured optical powers.

An optical amplifying apparatus and a method to control the same are disclosed. The apparatus includes a semiconductor device that integrates a variable optical attenuator (VOA) with a semiconductor optical amplifier (SOA). The VOA evaluates the optical power of an incident beam from a photocurrent generated therein. The attenuation of the VOA and the optical gain by the SOA are optionally determined based on the detected input power.