Hello! I am a student working on a portable laser project. The laser is going to be powered by two lithium-ion batteries at 3.4A capacity and 3.7 Nominal voltage (4.2 charging voltage cut-off and 2.5 discharging voltage cut-off). I'm using voltage regulators to step up or step down voltages for the components. I was informed by the optics student that he want to be able to vary the voltage to obtain different output power values. Unfortunately we've had problems with designing the laser since the 1064nm diode that we were going to use for the laser gave very poor results and we have to change that part. Now I am going to wait for my partner to decide on a laser pointer since this will be the next step. This information might not be useful right now but we were looking into powering the diode (1064nm) up to 1.8V max at a current of 640.104 mA. I wanted suggestions on how to power a diode or laser pointer and being able to lower and vary this voltage below that max voltage threshold. Should I used a voltage regulator and something after to vary the voltage or take a different approach?

 

There are many ways to drive a laser.
Normally I regulate the current not the voltage. Because small changes in voltage cause large changes in current. The light output is directly related to current and indirectly related to voltage. Also, the voltage is not temperature stable.
There are LED driver IC that will operate in the 3 to 6V input range and give you 640mA (adjustable). A "Buck" pwm will drop the voltage to 1.8V.