Laser diode optical wavelength control apparatus

A laser diode optical wavelength control apparatus comprising:

• a laser diode;
• optical branching means for branching a laser beam emitted by said laser diode into first, second, and third branched laser beams;
• a narrow-band first optical filter for receiving the first branched laser beam and transmitting a laser beam having a specific optical wavelength therethrough as a transmitted beam;
• second and third optical filters for receiving the second and third branched laser beams and transmitting laser beams having specific optical wavelengths therethrough as transmitted beams;
• first, second, and third photodiodes for converting output beams from said first, second, and third optical filters into electrical signals and outputting the electrical signals as analog voltages;
• comparator means for comparing the analog voltages output from said second and third photodiodes and outputting a signal representing a comparison result;
• differential amplifier means for performing differential amplification of a reference analog voltage obtained from said first photodiode and the output signal from said comparator means and outputting a control signal;
• a temperature adjustment element provided in tight contact with said laser diode and generating heat, a temperature of which is externally controlled;
• and
• temperature adjustment means for controlling the temperature of the heat from said temperature adjustment element on the basis of the control signal output from said differential amplifier means.