What are the wavelengths, frequencies or energies of the different
lasers used in a standard CD rewriter?

Hi sargant, 

An interesting question.  The short answer is that CD drives and CD-RW
drives use 780nm laser light (red) for both reading and burning.  The
only difference between the various modes of the drive is the power
output of the laser.

A CD-RW disc is made up of a number of layers. The number of layers
varies, but generally the structure (working from top to bottom) looks
like this:

Label             ---> 
==================================================
Reflective layer  ---> 
--------------------------------------------------
Dielectric layer  ---> 
..................................................
Phase change layer---> 
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Dielectric layer  ---> 
..................................................
Plastic layer     ---> 
==================================================
                                          ^
                        Laser beam        |
                                          |
                        Write head     <=====>

The phase change layer is made up of a heat sensitive dye compound.
When heated to one temperature and cooled it crystallizes, but when
heated to another temperature and cooled it becomes amorphous
(non-crystalline).  The phase change layer of a blank disc will be all
amorphous.  It allows light to pass through the layer to reflect off
the upper reflective layer (usually made of aluminum).  When the disc
has data on it, crystallized sections of the phase change layer will
absorb light instead of reflecting it, which registers as a data bit.

Depending on what the drive is doing it will use different levels of
power.  The lowest level of power is needed for reading, since it
doesn't need to do anything to the phase change layer.  The next
highest level is for erasing.  The operation involves heating the
layer just enough so that it becomes crystalline, allowing light to
pass through it.  The highest power is for writing, where spots on the
layer are made amorphous.

The actual power output that is needed varies depending on the speed
that the disc is being written.  The write operation requires the spot
on the disc be heated to around 600 degrees C, and for the erase
operation it must heat to around 200 degrees.  The faster the disc
spins the higher the power output will be needed in order to achieve
this temperature in the brief time that the spot is passing over the
laser.  To give you some idea of the power requirements, the maximum
power output of Sharp's GH5R385C3C 12x laser is 108 mW, of the
GH5R495A3C 16x laser it's 121 mW, and of the GH5R41HA3C 24X laser it's
144mW.  You can look at the specifications in detail here if you're
interested: http://www.sharpsma.com/sma/Products/Opto/Laser_diodes/Hologram_laser_diodes.htm

Incidentally, you may have noticed that CD-RWs often don't work in CD
player for audio recordings.  The reason is that they don't reflect
light as well as regular CDs or CD-Rs.  Newer CD players can adjust
their laser output to compensate for it, but older players may not be
able to detect any data on the disc because there isn't enough light
bouncing off it.

For an article about the various recording media technologies, visit
PC Tech Guide here: http://www.pctechguide.com/09cdr-rw.htm

Howstuffworks also has a good article:
http://www.howstuffworks.com/cd-burner4.htm

I hope this answers your question,

Hibiscus

Search Strategy: cdrw wavelength specifications, cd-rw red book, cd-rw
laser diode

Thank you very much - the first two links were especially useful.  The
paragraph about power output is the perfect answer I was looking for
(other non-scientific articles have confusingly referred to power as
"energy").  A great answer that went beyond what I had asked for.