Emission Frequency

In the case of a slow modulation and a weak current injection amplitude, noted as  i surrounding a medium injection current, noted as i0, the influence of the termal inertia of the environment is negligible. Thus, the modulation of the refraction sign and of the cavity length induced by thermal variation of the active environment via the injection current can be expressed by the following :

Where  is the cavity length for the current , the effective phase sign associates with  and a (positive) proportionality coefficient transforming the optical extension of the cavity by an increase in injection current via the temperature.

Let's consider a monomode laser diode emitting a frequency associated with the injection current . The differential of the relationship which gives the authorized emission frequency surround the state corresponding to the current , brings us to the expression of emission frequency without feedback upon the optical length of the cavity. Using the preceding relationship, we express it based on the injection current by :

It appears only in respecting the hypothesis of slow modulation and weak injection current amplitude, the emission frequency without feedback is linearly proportional to the injection current. The typical values for range from ‑300 MHz/mA to some -GHz/mA .