ECE 183 2012 Lab #3 Tunable laser diode (Agility)

λ(T0, I0) is a known wavelength at T0 and I0.
Generally it is sufficient to consider only the linear terms. For a precision of δλ/λ < 10 -6
the quadratic terms have to be respected. The equation is valid within a jump-free range.
The requirement of λ(T, I)= λc = const provides directly:
Fig.5. Laser power versus injection current with the temperature T as parameter.
Tunable Laser Diode
A tunable laser is a laser the output wavelength of which can be tuned. In some
cases, one wants a wide tuning range, i.e., a wide range of accessible wavelengths, while
in other cases it is sufficient that the laser wavelength can be tuned to a certain value.
Some single-frequency lasers can be continuously tuned over a certain range, while
others can access only discrete wavelengths or at least exhibit mode hopping when being
tuned over a larger range.
Fig.6 shows a schematic of the Sample-Grating, SG-DBR laser. It consists of four
waveguide sections longitudinally integrated together on the semiconductor substrate: a
gain section, containing an active layer embedded within a InP-based semiconductor
waveguide structure; front and back DBR mirror sections, formed by sampled gratings
which have been etched into passive (i.e. not containing active-layer material)
waveguides; and a phase section which contains neither gratings nor active material. All
four sections include electrical contacts. In the case of the gain section, current injection
controls output power. For the other three sections, injected carriers induce a change in
refractive index which tunes the lasing wavelength through shifts in DBR reflectance
spectra and the cavity mode spectrum.
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