Systems and methods herein provide for a diode laser system that improve cold laser therapy. One cold laser therapy device includes a laser diode operable to propagate laser pulses towards a person's skin, a first driver operable to drive the laser diode to propagate the laser pulses within a first range of laser pulse rates, and a second driver operable to drive the laser diode to propagate the laser pulses within a second/higher range of laser pulse rates. The device also includes a controller operable to process an instruction to tune a laser pulse rate of the laser diode from the first range of the laser pulse rates to the second range of the laser pulse rates, to disable the first driver in response to the instruction, and to enable the second driver in response to the instruction.

Systems and methods for controlling laser modulation in burst communications. In a start-up phase, a drive circuitry sequentially applies first and second drive currents to a laser diode such that it produces a first and second optical output, respectively. A compensating current source coupled to the laser diode provides a current related to the first and second drive currents to maintain a combined current flowing through an impedance connected to the laser diode at a substantially constant level during the start-up phase. An optical sensor measures the first and second optical outputs, and a controller uses values of the first and second drive currents, the outputs from the optical sensor, and at least one supplied input value to provide control values for the drive circuitry for controlling operating current of the laser diode during a subsequent operating phase, wherein information is transmitted in at least one burst.

A device for modulation of an optical signal includes an active layer configured to provide electrically controlled gain of the optical signal; an electrode layer arranged to extend along the active layer, wherein the electrode layer comprises a plurality of separate electrodes associated with respective parts of the active layer, wherein each electrode have a size of a cross-section in the electrode layer smaller than a wavelength of the optical signal and neighboring electrodes are separated by a distance smaller than the wavelength of the optical signal; wherein an electrical signal to each of the electrodes is controllable for locally modulating an imaginary part of a refractive index of the active layer by locally controlling an electrical signal in the active layer.

By eliminating the need to use a high-precision clock in pulse width detection for pulse width adjustment in a case where light-emitting elements as vertical-cavity surface-emitting lasers are pulse-driven, circuit configuration is simplified and cost is reduced. A laser drive apparatus according to the present technology includes a drive circuit unit that drives light-emitting elements as vertical-cavity surface-emitting lasers to emit light on the basis of a pulse signal, a pulse width detection unit that detects the pulse width of the pulse signal on the basis of the potential of a capacitor when the capacitor is charged on the basis of the pulse signal, and a control unit that performs control so that the pulse width is adjusted on the basis of a detection result of the pulse width.