Hi Folks,
I was fortunate enough to secure a small quantity of very-high quality 100+ mW, 532 nm DPSS laser pens made by Shanghai Institute of Optics and Fine Mechanics ( Shanghai Daheng Optics and Fine Mechanics Company, Ltd.), model DHL GB-100. These are the finest quality laser pens I have seen so far at any price, and represent the upper limits of what is possible given the state of the art in 12mm DPSS lasers, in my humble opinion. I recently distributed four of these units to the CPF membership, and am expecting further review and input from those members after they have had a chance to look them over. I am not a dealer of laser pens, but I do integrate the units into OEM devices that I manufacture. The intent of this article is simply to offer an impartial technical appraisal of the unmodified devices as-built.
All of the units I purchased measured anywhere from 102 to 120 mW peak on my Coherent Lasercheck. Peak power is achieved after only 5 seconds typically from a cold start, and maximum continuous operating time is specified as 45 seconds. Power de-rates gracefully to about 10-15% below maximum on average at the highest operating temperature. In intermittent operation, the proper ON/OFF ratio appears to be about 1:4 to keep the output power in the high-power portion of the power vs. temperature characterstic curve. I have not tried thermo-electric augmentation yet.
I know that many of you collect lasers for the challenge and fun of modifying and tweaking. This unit is not one to experiment with for two reasons: First, there is no advantage in doing so. The units are already peaked for maximum performance right out of the box. Secondly, the units are built so solidly that it is extremely difficult to take them apart. I sacrificed two of mine in the name of science and good old-fashioned American reverse-engineering, only to discover that there is no way to peak them any further. The pen barrel has a really nice pearl-grey, deep gloss finish with gunmetal-chrome trim and pocket clip. I had no other choice than to destroy the pen barrel by cutting in two different places with a miniature pipe cutter to access the laser module. I have taken a lot of laser pens apart. Unless you are very skilled and very careful, you will be lucky to still have a working unit if you try to take this one apart. Trust me on this! (yes, I have a dead one).
Quality of the units is evident in every aspect of the laser assembly. For example, there is a locking set-screw to fix the LD in place after factory alignment, rather than the typical spin-on lock ring that inevitably moves the LD out of the optimum position during tightening. The focus barrel and LD holder threads are tight and were cut accurately. The MCA input and output lenses are K-9 glass, as is the objective lens. The unit is well filtered against infra-red emissions, and produces nearly all of its output power at the 532nm line. The alignment of the optical components is such that the output beam is nearly perfectly coaxial. Alignment of the LD is already optimized in the X-Y and rotational axes with respect to the large (2.5mm?) MCA. The PCB is well supported within the pen barrel by a plastic shoe that fits snugly around the board, flush to the inner surface of the pen, to prevent damage by pushing the ON button too hard. There is a potentiometer on the PCB, but it is already set for optimum performance and efficiency. Advancing the control only increases current consumption of the regulator without increasing output power. However, power may be reduced with this control. I was able to reduce power as low as 45 mW before experiencing mode-ing on most units. One must use care not to short the control to the case during adjustment....this will cause instantaneous destruction of the laser diode. (yes, I ate one).
Quality of the product extends to the driver board as well, which is beautifully silkscreened and conformally coated....a really nice job for such a small PCB. The regulator circuit is reverse-voltage protected by a diode in series with the battery supply, and current regulation appears to be achieved with the popular current-mirror method. There is no optical feedback or other APC circuit, so the driver holds the LD voltage and current constant over the entire duty cycle. Surprizingly, output power stability is quite good, which I attribute to the design of the MCA/optical cavity and LD holder. The design offers a much more effective heat-sink for the LD and MCA than other designs I have seen, somewhat dampening the effects of heating upon output power. The assembly draws about 650 mA of current from a 3VDC source ( two AAA Lithium photo-type cells). Considering that the unit dissipates nearly two Watts in operation, it is amazing that output power stability is as good as it is, given that there is no optical feedback. It seems clear that the designers chose to address the problem of power stability at it's source - heat management - rather than to build a more complex, less efficient, and more expensive optical feedback topology. Lifetime of the laser is rated at greater than 5000 hours, and may perform well beyond that due to the effectiveness of heat transfer from the LD and crystal assembly. In addition, the LD itself is a 9mm type rather than the 5.6mm cans typically found in lasers of this power class.
Beam characteristics are excellent, with diameter <<1mm and divergence at <1.2 milliradians. I have not determined the coherence length of the beam nor investigated the unit's suitability for holographic purposes, but it is obvious even by visual inspection that the units exhibit very low-noise for the type, and may be useful for holography or other lab work. This is an extraordinary statement to make about any DPSS laser pointer, as many of you will already understand. As I said, I believe that these units are the best available in a 12mm laser pointer. (Why can't America produce something as good?)
The pens are available at retail in the US from ultralasers.com, and can be found on eBay by seller shawnwang. I am curious to know if other CPFers have gained experience with these units yet, and what your impressions and observations have been, so please add your comments!
Cheers All,
Lew
I was fortunate enough to secure a small quantity of very-high quality 100+ mW, 532 nm DPSS laser pens made by Shanghai Institute of Optics and Fine Mechanics ( Shanghai Daheng Optics and Fine Mechanics Company, Ltd.), model DHL GB-100. These are the finest quality laser pens I have seen so far at any price, and represent the upper limits of what is possible given the state of the art in 12mm DPSS lasers, in my humble opinion. I recently distributed four of these units to the CPF membership, and am expecting further review and input from those members after they have had a chance to look them over. I am not a dealer of laser pens, but I do integrate the units into OEM devices that I manufacture. The intent of this article is simply to offer an impartial technical appraisal of the unmodified devices as-built.
All of the units I purchased measured anywhere from 102 to 120 mW peak on my Coherent Lasercheck. Peak power is achieved after only 5 seconds typically from a cold start, and maximum continuous operating time is specified as 45 seconds. Power de-rates gracefully to about 10-15% below maximum on average at the highest operating temperature. In intermittent operation, the proper ON/OFF ratio appears to be about 1:4 to keep the output power in the high-power portion of the power vs. temperature characterstic curve. I have not tried thermo-electric augmentation yet.
I know that many of you collect lasers for the challenge and fun of modifying and tweaking. This unit is not one to experiment with for two reasons: First, there is no advantage in doing so. The units are already peaked for maximum performance right out of the box. Secondly, the units are built so solidly that it is extremely difficult to take them apart. I sacrificed two of mine in the name of science and good old-fashioned American reverse-engineering, only to discover that there is no way to peak them any further. The pen barrel has a really nice pearl-grey, deep gloss finish with gunmetal-chrome trim and pocket clip. I had no other choice than to destroy the pen barrel by cutting in two different places with a miniature pipe cutter to access the laser module. I have taken a lot of laser pens apart. Unless you are very skilled and very careful, you will be lucky to still have a working unit if you try to take this one apart. Trust me on this! (yes, I have a dead one).
Quality of the units is evident in every aspect of the laser assembly. For example, there is a locking set-screw to fix the LD in place after factory alignment, rather than the typical spin-on lock ring that inevitably moves the LD out of the optimum position during tightening. The focus barrel and LD holder threads are tight and were cut accurately. The MCA input and output lenses are K-9 glass, as is the objective lens. The unit is well filtered against infra-red emissions, and produces nearly all of its output power at the 532nm line. The alignment of the optical components is such that the output beam is nearly perfectly coaxial. Alignment of the LD is already optimized in the X-Y and rotational axes with respect to the large (2.5mm?) MCA. The PCB is well supported within the pen barrel by a plastic shoe that fits snugly around the board, flush to the inner surface of the pen, to prevent damage by pushing the ON button too hard. There is a potentiometer on the PCB, but it is already set for optimum performance and efficiency. Advancing the control only increases current consumption of the regulator without increasing output power. However, power may be reduced with this control. I was able to reduce power as low as 45 mW before experiencing mode-ing on most units. One must use care not to short the control to the case during adjustment....this will cause instantaneous destruction of the laser diode. (yes, I ate one).
Quality of the product extends to the driver board as well, which is beautifully silkscreened and conformally coated....a really nice job for such a small PCB. The regulator circuit is reverse-voltage protected by a diode in series with the battery supply, and current regulation appears to be achieved with the popular current-mirror method. There is no optical feedback or other APC circuit, so the driver holds the LD voltage and current constant over the entire duty cycle. Surprizingly, output power stability is quite good, which I attribute to the design of the MCA/optical cavity and LD holder. The design offers a much more effective heat-sink for the LD and MCA than other designs I have seen, somewhat dampening the effects of heating upon output power. The assembly draws about 650 mA of current from a 3VDC source ( two AAA Lithium photo-type cells). Considering that the unit dissipates nearly two Watts in operation, it is amazing that output power stability is as good as it is, given that there is no optical feedback. It seems clear that the designers chose to address the problem of power stability at it's source - heat management - rather than to build a more complex, less efficient, and more expensive optical feedback topology. Lifetime of the laser is rated at greater than 5000 hours, and may perform well beyond that due to the effectiveness of heat transfer from the LD and crystal assembly. In addition, the LD itself is a 9mm type rather than the 5.6mm cans typically found in lasers of this power class.
Beam characteristics are excellent, with diameter <<1mm and divergence at <1.2 milliradians. I have not determined the coherence length of the beam nor investigated the unit's suitability for holographic purposes, but it is obvious even by visual inspection that the units exhibit very low-noise for the type, and may be useful for holography or other lab work. This is an extraordinary statement to make about any DPSS laser pointer, as many of you will already understand. As I said, I believe that these units are the best available in a 12mm laser pointer. (Why can't America produce something as good?)
The pens are available at retail in the US from ultralasers.com, and can be found on eBay by seller shawnwang. I am curious to know if other CPFers have gained experience with these units yet, and what your impressions and observations have been, so please add your comments!
Cheers All,
Lew
............ sigh....
