Page 260 - An Introduction to Microelectromechanical Systems Engineering

Types of Packaging Solutions 239

Figure 8.11 Modified by brazing two tubes to the header and the cap, the TO-8 metal can
become suitable for packaging fluidic microdevices, such as this microvalve from Redwood
Microsystems. (Courtesy of: A. Henning, Redwood Microsystems of Menlo Park, California.)

plate sits on a first thermoelectric cooler (TEC) that controls the temperature of the
DFBs and performs the fine tuning of the output wavelength. The two beam splitters
sample a fraction of the laser light (typically less than 1%) onto the quadrant detec-
tor to feed the spatial position of the beam back to the electronics that control the
angles of the micromirror.
An etalon and a standard detector epoxied on a second TEC play the role of a
built-in wavelength locker [see Figure 8.12(b)]. A fraction of the light sampled by
the beam splitters passes through the etalon onto the detector for locking to the ITU
grid (see Chapter 5). A second TEC maintains the temperature of the etalon to a pre-
determined value.

Tilting
micromirror
Etalon
Quadrant detector TEC 1

Fiber DFB array
DFB array

Beam Beam
TEC splitter splitter
Quadrant
detector
Beam splitter
2 Etalon
TEC
Tilting micromirror
subassembly
Detector

(a) (b)
Figure 8.12 (a) A rendering of the packaging for the tunable laser from Santur Corp.; and (b) a
block diagram of the components within the packaging of the tunable laser. A first thermoelectric
cooler controls the temperature of the DFB array. A second cooler controls the temperature of an
etalon and a detector that act as a wavelength locker.