I am a relative newby here at the forum, but not new to lasers.
Cyparagon is pretty spot on in his assessment. I would add to this that commercial lab lasers are designed for many and varied purposes. They are generally designed to operate stably for long periods of time without mode shifts, at stable power so that they can perform in a variety of demanding tasks with little maintainence. Some lab lasers may be purpose designed for a narrow research purpose. Depending on the end use, they may even allow access to the inside of the resonator cavity to permit tuning or tinkering the optical path inside the resonator. What you want to design all depends upon your end use. Do you want to do experimentation with optical physics and materials? Holography? scanning and light shows? welding and cutting? or just popping balloons and lighting matches? Depending on your use, you may want linear or random polarization, clean TEM00 mode, continuous or pulsed operation, long life, or long coherence length.
Some applications require very stable laser, others are not so critical. For stability, control of the temperature of the various elements is especially important, hence the big heatsinks. Temperature will affect the dimensions of the resonator, the mobility of carriers in the semiconductor and the properties of the lasing transitions within the lasing medium. Control of the power output is not too difficult for diode lasers by using active optical feedback and/or active temperature control as long as the laser is operated well under it's maximum rating and held at a stable operating temp. If you just want short term stability, you can operate most diodes with (a moderate) constant drive current or constant drive power, and a big heatsink. If you know some electronics, this should be no problem - you will need to avoid overcurrent, current overshoot, esd, transients, and reverse current at all costs or you will make a crappy LED out of your laser diode.
Lasers such as the diode pumped 532nm greens use additional elements such as Yag and KTP crystals to convert a high power IR diode laser output (808nm) to a usable frequency to pump the YAG (1064nm), then double the frequency to get 532nm green. Stable green lasers are much more difficult to design as a result.
You may want to peruse Sams laser faq - just google [sams laser faq diode laser]. Also, you might want to download and read through some laser diode specs - they all operate pretty similarly, basically a forward biased diode junction, albeit at different threshold currents and operating points. Like blue leds, shorter wavelengths laser junctions operate at higher bandgap energies, hence need higher forward voltages to get to the operating current level. You can google GH04P21A2GE and find a high power violet diode datasheet to study at the Sharp microelectronics website. High power reds or IR's operate at lower forward voltage drops but may have much higher currents depending on power.
< I've been doing this for stuff for 30 years and you asked for not "really simple"
>
be afraid - be careful!
