Page 467 - Tunable Lasers Handbook

8 Tunable External-Cavity Semiconductor Lasers 427

Ahfilter= 0. 22xAhSol a43.00 Rfacet" 0.001 ReXt= 0.20
- 1 I
0.8-
4

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
CHANGE IN FILTER WAVELENGTH (Afilter - Ao) /
FIGURE 46 Calculated tuning curve for 20% external feedback, 0.1% coated-facet reflectance,
linewidth broadening factor = 6. filter bandLYidth = 0.22 times solitary mod? spacing.

ing fidelity can be characterized by the rms residual of a linear fit to the calcu-
lated or measured tuning curve [46].

7 7. CONSTRUCTION AND PACKAGING

Packaging means taking construction of a laser beyond the optical bread-
board stage. Packaged designs should be capable of operation in laboratory or
production environments without the need for readjustment duz to normally
expected vibrations. microphonics or temperature fluctuations. Packaged lasers
can be divided into two categories: laboratory modules and full instruments. Lab
modules are suited for laboratory research work. They may require some manual
adjustments and additional support apparatus such as current sources. motor
drives, and wavelength meters. Instrument-grade ECLs are fully self-contained.
programmable, do not require optical bench siting. and meet the requirements
for automated test and measurement work.
An early (1975) packaging effort at Lincoln Laboratory [57] resulted in a
laboratory module that featured a tuning knob with a mechanical readout gauge