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Emission Questions & Answers
- What are the main characteristics of xenon flash lamps?
- How does a deuterium-lamp-based VUV ionizer remove electrostatic charge in vacuum conditions?
- How does Hamamatsu measure the directivity of pulsed laser diodes (PLDs)?
- What is a “3-stack” PLD?
- Do you have any recommended driving conditions to achieve a longer life for packaged PLDs?
What are the main characteristics of xenon flash lamps?
Xenon flash lamps are pulsed sources that emit a broad wavelength of light from 160 nm to approximately 7500 nm, so one light source (instead of multiple sources) can be used to generate light from UV to infrared. Their output intensity at UV wavelengths is especially high.
They also have advantages over continuous emission discharge lamps. For example, they don't require a long warm-up time, so they can be used right away after being turned on. Because they emit less heat than other types of lamps, they are ideal for designing and developing new instruments.
How does a deuterium-lamp-based VUV ionizer remove electrostatic charge in vacuum conditions?
A VUV ionizer contains a deuterium lamp that emits vacuum ultraviolet (VUV) light shorter than 200 nm, so the emission has high energy, about 10.78 eV. When absorbed, this high-energy light can ionize residual atoms and molecules in a vacuum condition. The ionized atoms or molecules are then attracted to charged surfaces, effectively neutralizing the charge.
In vacuum conditions, VUV light is more effective in removing electrostatic charge than x-rays because atoms and molecules have higher absorption coefficient for VUV than x-rays. Although x-rays have higher energy, they are more easily transmitted. So when there are fewer atoms and molecules available to ionize (such as in vacuum conditions), the absorption coefficient plays an important role.
How does Hamamatsu measure the directivity of pulsed laser diodes (PLDs)?
A photodiode with a slit is scanned in an angular direction around the PLD to capture the relative intensity profile as a function of angle. The slit is set to a 1.0 deg. and 0.2 deg. resolution. See the figure below for an example directivity plot.
What is a “3-stack” PLD?
A 3-stack pulsed laser diode consists of three laser chips stacked on top of each other to make a single structure. It isn’t a single chip divided into three regions. We’ve found that having a stack of three chips results in optimal emission area efficiency.
Do you have any recommended driving conditions to achieve a longer life for packaged PLDs?
Failure modes for packaged PLDs can be caused by assembly distortion, solder migration, and crystal defects. These stressors are affected by the operating current, duty cycle, and operating temperature, so these operating conditions should be relaxed as much as possible to prolong the lifetime of the device.
If you have a technical question you’d like to see answered on this page, email us.
Meet the engineers
They say “a rolling stone gathers no moss.” But, Applications Engineer Masakazu “Moss” Kawazu decided to plant himself in the US for a few years and serve as our expert in light source and lamp futures. Originally from Japan, Kawazu is a big soccer fan and especially enjoyed all the exciting action of the World Cup this summer.
Mohamed is an Applications Engineer and optics expert, specializing in optical systems and lasers. He started reading and learning about the cosmos at a very early age, and that’s what drew him into studying physics and specializing in optics. When he’s not looking up at the sky wondering about the fabric of the universe, he can be found driving up and down mountain ranges chasing the most expansive vistas he can find.
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