Laser device and method of determining a malfunction of a laser diode

A laser device, comprising

• a laser diode configured to emit radiation, wherein an output power of the radiation is dependent on a laser diode driving current;
• a photodiode configured to receive the radiation emitted by the laser diode, wherein a photodiode current induced in the photodiode by the received radiation is dependent on a power of the received radiations;
• and
• circuitry configured to:
• measure first photodiode current values for at least two first laser diode driving current values at which the laser diode is in a non-lasing operation,
• calculate a first linear slope from the measured first photodiode current values,
• measure second photodiode current values for at least two second laser diode driving current values at which the laser diode is in a lasing operation,
• calculate a second linear slope from the measured second photodiode current values,
• determine a calculated laser threshold current of the at least one laser diode as the laser diode driving current value at which the first and second linear slopes intersect,
• determine a ratio of the gradient of the second linear slope to the gradient of the first linear slope, and
• detect a malfunction or degradation of the laser diode when the ratio is equal to or lower than a threshold.