Maybe it is because most people can't "see" it to believe it.
Are you modulating it by varying the current, using a detector to generate negative feedback? As I recall most electro-optical semiconductor devices, emiiters or detectors, are current devices and not voltage devices. I was doing work with SS lasers and had to make accurately controlable current sources as well as using a peltier SS heat pump salvaged from a auto type refidgerator/cooler to hold the heatsink within .5 Degrees C of the desired operating temperature to maintain mode control of the laser. The laser was used in a portable interferometer and had to be held to mode and frequency. the buggers tend to mode hope otherwise. Ours was a 1 Watt unit, replacing an older HE-NE type, but was visible deep red.
Sounds neat!
rob
Low speed modulation or basic diode power control (up to a few Hz) can be done by varying a control voltage from 0 to 10V. The control voltage can be set to control the output power or the diode current. The current or power is controlled precisely inside this loop and output voltages indicate 0-2 watts (800nm) with a voltage of 0-10V for use as a readout.
The two diodes frequency are regulated by TE coolers and the beams are combined with a dielectric mirror. The final mode is locked to 00 by the pump method, being end fed into the volume of the crystal axially via fiber. The crystal head and optical cabinet can be heated by a strip heater (I do not have) to keep power stability. It was run at 85 deg F. The diode power supply also contains the Q-switch driver and control inputs for it. I have jumpered the control/interface board I made to set for CW, no Q-switch and 2 watts diode output.
DC to ?MHz modulation is by RF-driven AO modulator after the Nd:YLF crystal and after the Q-switch. I have the drive amplifier which can be driven by a signal generator set for AM with external input so the bandwidth is limited only by the generator (the AO modulator works at around 60 MHz), or the level can be controlled at this point by using one of the power sensors in a feedback circuit (application specific feedback circuit absent) to feed back the 0-10V level to the diode pump. Everything is themperature controlled or controllable for stability.
This was used to trim semiconductors using the 1047nm output of the Nd:YLF crystal so interferometry stability was not required of the power level. I have everything from the ac cord to the focusing lens, with the exception of the X-Y gross positioning robot and its electronics, the electronics used to select one of several ND filters, control the beam size steppers, and to drive the pair of galvos which adjust the the beam path through the lens. All these things add up to this being able to write characters on semiconductor dice or chips.
The gross and fine positioning system used a Zygo stabilized HeNe laser and two interferometers to position the cutting head and beam spot to within 350nm in the X and Y planes. I have this laser also and all the optics (two interferometers, beamsplitter, a few adjustable beam handling mirros, and two receivers that would connect to the interferometer electronics). manuals too.
All this stuff works and is fresh from the wafer sort clean room. A good find! I have already burnt some holes in cardboard.
I believe I will sell or trade the items off, to make room for some other stuff. I would like to find a 10-20W CO2 laser with low divergence and a 12V/28V power supply for same. I found a receipt for the "power supply" (precision regulated diode system, R2 type) section alone -something over $25K. Amazing what stuff cost new.
About the deep red color, if the system you were using was infrared but you saw the beam spot, that could have been the interpretation of the eye. Beyond 680nm, the eye respons really drops to almost zero. Some people can see a safe 780nm beam spot faintly, but no one I know of has seen 800nm or 808nm until it is too bright for safe viewing of the diffuse reflection. The 800nm and 1047nm beams apear to be deep red but it is a trick because only the red-seeing cones respond, and then only weakly. By the time the IR power is quite high so that a deep red spot at these wavelengths is visible, one is actually viewing a blazingly intense spot of infrared light on the target. It is very dangerous because the eye does not react to the extreme brilliance by narrowing the pupil, it sees only a dim red glow and damage can be done by retinal heating, the worker is unaware till they might have a splitting headache later or sudden onset of vision problems. I have a set of IR protective goggles and I use a video camera to show where the beam is landing.
