Welcome, viewers of Science and Spirituality. Today we will be meeting Dr. Federico Capasso, a Robert L. Wallace Professor of Applied Physics at the Harvard School of Engineering and Applied Sciences.

Over the years, Professor Capasso has become primarily known from his pioneering work on novel quantum devices such as avalanche photo-detectors, which are light sensors that process optical communications to electrical signals, resonant tunneling diodes, ultra-fast transistors, and other semiconductor devices.

The Quantum Cascade (QC) Laser is an innovation Professor Capasso and colleagues developed in the early 1990s. This technology holds promise for important applications such as sensing gas and liquid vapor molecules in various environments with ultra high sensitivity - even to the degree of one part per billion. Given that we live in times of accelerating global warming, our world needs such a tool, especially for measuring the greenhouse gas concentrations in the atmosphere.

Supreme Master Television interviewed Dr. Capasso to learn about the highlights of his scientific journey through the world of quantum devices, and how these tools can impact our lives. Dr. Capasso begins by giving us a bit of his background.

I got my doctorate over in Italy in the late 70s. I got a fellowship for the US for nine months. So I decided to go to the great Bell Laboratories, that for decades has been essentially the prime industrial laboratory in the whole world. Seven Nobel Prize winners. It invented the transistor, the laser, the fax machine, the feedback circuit, the stereo sound, and so forth. And I ended up staying there for 27 years. I was a researcher for about 10 years, and I became a manager. In my last two years, where I was vice president for Physical Research; and at the end of my 27th year there I decided it was time to do something else. I moved to Harvard, and I’m having a great time. Starting from the early 1980s, scientists were able to implement quantum wells, resonant tunneling, 2- and 1-dimensional electronic systems, with electrons barely subjected to impurity scattering, because semiconductor materials could be made so pure. This was thanks to a powerful crystal growth method called Molecular Beam Epitaxy (MBE), capable of growing high crystalline quality thin layers with atomic accuracy, and high material purity.

Thus, at that time, scientist-engineers like Federico Capasso had access to resources to create imaginative quantum devices, based on abstract ideas taken from quantum physics textbooks They also explored new avenues of electronic and photonic devices, practically limited only by their imaginations.

The idea basically is using the laws of quantum mechanics, you can think of yourself like a modern alchemist. You can, using the laws of quantum mechanics, tailor-grow materials in a controlled way.

So that you can create materials with man-made properties. And in fact the Quantum Cascade Laser is an exercise in design of a new class of laser material. Nature is involved because it dictates the laws of quantum mechanics, but essentially women and men are really the designers behind it. We design things so that a new material has certain properties that you cannot find in nature.

For many decades double-heterostructure laser diodes have been manufactured and this technology greatly advanced the world’s semiconductor and telecommunication industry in the 1980s and 1990s. German scientist Dr. Herbert Kroemer, and Russian scientist Dr. Zhores Alferov were named Nobel laureates in physics in 2000 for developing semiconductor heterostructure lasers and other devices used in high-speed opto-electronics.

In 1994, Professor Capasso and his Bell Labs colleagues invented a new type of laser family, called the Quantum Cascade (QC) Laser, which can be pictured as an electronic waterfall flowing down a staircase. At each step, a photon of a certain wavelength is emitted.

Another special attribute of this laser is that wavelength emissions can be altered over a broad wavelength range in the mid-infrared wavelength range (3-12 micrometers) where it’s not easy to find alternative efficient light sources. And it is an important spectral range because that is where most molecules have exhibited their absorption and luminescence spectra, thus allowing the laser to be used for chemical analysis.

The semiconductor laser essentially has entered everyday life. I mean, when you listen to music on a DVD, basically what reads the DVD is a semiconductor laser. It’s also used for telecommunications; we wouldn’t be seeing high speed communication - the fact that we can literally transmit the Encyclopedia Britannica in maybe just a few minutes over high speed cable – without a semiconductor laser, because what it does is it emits pulses of light that are on and off. They represent bits.

Now, the semiconductor laser is based on a very simple principle basically. The wavelength that it emits depends on the chemical properties of the material. So, if you want to have a blue laser you choose a material called gallium nitride. But if you want an invisible semiconductor laser like you use for telecom type of applications, you have to change the material and use complicated alloys.

It’s called indium gallium arsenite phosphite. So, you want to change the color of the laser, you have to change the material.

Professor Capasso noted that the Quantum Cascade Laser is a huge step forward in terms of laser design.

Basically, you control the wavelength not by changing the material, but by changing the thickness of the ultra-thin layer inside the active region. The active region is the region that emits the laser light. And so, it is designed to cover primarily the so-called mid-infrared spectrum. This is the spectrum where the molecules have their telltale absorption fingerprints. Molecules like carbon monoxide, carbon dioxide, water, and so forth.

So the mid-infrared is a potentially extremely important technological area because, using these invisible wavelengths, you can detect molecules. So, these lasers detect very low concentrations, parts per billion in volume trace gases. These could be good trace gases, they could be bad ones, toxic ones. So the applications are potentially huge for this laser.

When Science and Spirituality returns, we’ll explore more on how the Quantum Cascade Laser could be used as a tool to measure pollutants in the atmosphere. Please stay with us.

Welcome back to Science and Spirituality where we have been hearing from Professor Federico Capasso about the invention of the Quantum Cascade Laser. This tool can emit coherent light in the mid-infrared range, where many gas and liquid molecules have their characteristic absorption spectra. Even one molecule per billion can be detected using this novel laser light source in various environments. Let’s continue the Quantum Cascade Laser story with our guest, Professor Capasso.

This is the heart of the Quantum Cascade Laser. You see, by controlling this very thin layer, you are seeing a cross section. Take a cross section of a cake, or a sandwich. These are the layers of the sandwiches. So what happens is you inject current. This is the blue arrow, and you have an electron, which is a unit of an electrical current stumbling down this energy staircase.

At every stage you emit a photon, and so you when the electron traverses the staircase, you have 10-20 photons per electron. So this can be a very powerful laser. We are collaborating with a company in California now, Pranalytica, and we made this very powerful laser with them that gives out 3 watts of power in actual continuous wave, at mid-infrared wave length.

Dr Capasso next speaks about other real world applications of the laser.

This is a beautiful collaboration we had with Ford Motor Company. We want to make sure that cars do not emit too much bad gases, like carbon monoxide and nitrous oxide and so forth.

Now in the future, as the problem of climate and pollution becomes more severe, the rules, at least in the US, will become more and more stringent. So we are looking to be able to measure parts per billion of certain gases in the exhaust of automobiles. This is another beautiful type of application.

We are collaborating here at Harvard with one of the world leaders of atmospheric chemistry, Professor Gene Anderson. He was instrumental in writing the Montréal Protocol for the ozone hole. We are starting to send our laser in the actual stratosphere and in the high atmosphere to measure tiny concentration of gases.

These are like methane that are markers of the jet stream. It turns out if you measure the concentration with height of these gases you can determine the path of the jet stream. And in fact this is a collaboration we did with NASA (National Aeronautics and Space Administration). This is an aircraft that went up to 20,000 kilometers.

And our QC lasers were right here, under the wing, and we measured the concentration of methane at parts per billion level as the aircraft was going up and diving down. We need to understand the climate. This is a very serious problem. For example, this is a model that tells what the sea level rise induced by global warming could do to Greenland. You see, this is a scenario of Greenland melting. Three meters of sea level rise, it could be serious.

So, climate is affected also by the circulation of even small concentrations of gases in the atmosphere. And so the idea here is to send out QC lasers. These are UAVs, Unmanned [Aerial] Vehicles. There’s no pilot. The QC laser will be sitting here and measure very tiny concentrations of these gases, to understand and research their effect on the climate. Eventually we need a predictive model of climate, so these types of measurements can help in this direction.

It appears the Quantum Cascade Laser can help better our world in many ways, especially in the area of climate change. We thank Professor Capasso for sharing his insights on this high-level technology that he helped develop.

Please join us next Monday, for part two of our program where Dr. Capasso will discuss the esoteric Casimir–Lifshitz effect with us. Coming up next is Words of Wisdom, after Noteworthy News, here on Supreme Master Television. May your life be blessed with God’s love, comfort, and light.

Wonderful viewers, welcome to Science and Spirituality. On today’s episode, we will be continuing our discussion with our featured scientist from last week’s program - Dr. Federico Capasso, a Robert L. Wallace Professor of Applied Physics at the Harvard School of Engineering and Applied Sciences in the USA.

Over the years, Professor Capasso has become primarily known for his pioneering work on novel quantum devices such as avalanche photo-detectors, which are light sensors that process optical communications to electrical signals, resonant tunneling diodes, ultra-fast transistors, quantum cascade lasers, and other semiconductor devices.

Recently he made a splash in the scientific world when he and his research team observed a repulsive, instead of the normally attractive, quantum force from the so-called Casimir effect. A possible future application of this phenomenon is the ability to make nano, or extremely small, objects levitate. This new finding was the cover story of the January 2009 edition of the prestigious scientific journal “Nature”.

In an interview with Supreme Master Television, Dr. Capasso explains more about this important discovery. Now let us join the discussion. In 1948, there was a relatively famous Dutch physicist by the name of Casimir. He had been working with Niels Bohr in Copenhagen, world famous physicist. And he was working then at the Philips Research Laboratories. And there were some data in the lab they could not understand.

So, out of an interesting chain of thinking, Casimir, out of the blue, came out to propose his famous Casimir effect. You take two metals; there is no charge on these two metals. Two metals are like my two hands. Now we know that if there is a positive and negative charge they attract each other. If there is a same charge, positive/positive, they repel each other.

Now he said, take two neutral metals, put them close enough. What does he mean close enough? Hundred nanometers distance. So one nanometer, one billionth of a meter. Then he said, quantum mechanics tells you that they will attract each other even though there is no charge. When he proposed this, some people were thinking, “this sounds so crazy,” and the math was kind of very difficult. But then he provided a physical explanation.

In the old days of classical mechanics, a vacuum was what remained if you emptied a container of all its particles and lowered the temperature down to absolute zero. However, the notion of a vacuum has completely changed with quantum physics - as now we know that the vacuum is not empty. All fields, in particular electromagnetic fields, have fluctuations even in a vacuum with temperature at absolute zero. We call this vacuum energy, or zero point energy.

The force discovered by Dr. Hendrik Casimir is another example of the spectacular manifestation of vacuum energy fluctuations. Professor Capasso next discusses the Heisenberg Uncertainty Principle and links it with vacuum energy and Casmir effect. In quantum mechanics, there is not a state of absolute rest. So there is nothing like an atom at rest, a molecule at rest, even if you are at zero temperature, and you can go arbitrarily close to a zero temperature but never reach it.

There is an inherent motion that will never stop, no matter how you actually cool the matter. These metal plates, if you look at one metal, it’s true that the charge is zero. But in time, because of this continuous motion of the electrons, we know that metals have electrons that are negatively charged particles that can move around freely. And there is a background of positive ions. So the metal is actually neutral.

But what happens is that the electrons fluctuate because of this motion. So on these plates you have charged fluctuation. On the actual surface, you might have an imbalance of charge, on one side of the plate you might have a patch of positive charge; on this side you might have a patch of negative charge, right? On the other plate which is in front I will find the opposite side of charge. I have positive here, negative here. Positive here where there is negative here. So, there is going to be a small attraction, because of this charge fluctuation.

And the fascinating thing is, between any microscopic objects, these forces are not only between metals. If I take a book like this and a book near here, and put it very close, there is going to be, if I put them very close, a similar force, much weaker than in the cases of metal. So this is a universal force, this Casimir force that is between any macroscopic or microscopic bodies, starting from molecules, going up to macroscopic things.

When we return, we’ll continue with the amazing Casmir force, which originates from quantum fluctuations or vacuum energy.

Welcome back to Science and Spirituality where we are exploring the Casimir force. Our guest today is Professor Federico Capasso, a Robert L. Wallace Professor of Applied Physics at the Harvard School of Engineering and Applied Sciences. The Casimir force is an important factor to consider when we try to scale down machines into such tools as Micro Electromechanical Systems (MEMS) or even to nano-scale mechanical systems.

The attractive Casimir forces could make things stick together and possibly jam the machinery. Micro Electromechanical Systems are typically micrometer scale devices, and are commonly used in many industries. This is a micromachine that we made at Bell Labs. This was in 2000. I just had heard so much about the Casimir effect, and said, “How am I going to measure it?”

Simple! I had my colleagues at Bell Labs make for me this Micro Electro Mechanical System (MEMS). What is MEMS? It’s important! Absolutely! Your airbags. I hope you are never going to have an accident. But if all of a sudden crash or to suddenly stop your car, the airbag pops out and makes sure you don’t get crushed against your steering wheel. And what controls this is a MEMS device. So MEMS are in everyday life.

So essentially, they are chips that have mobile parts. You see, this is a seesaw; it is essentially made in silicon, but it is all gold. And then we got a sphere which is metalized of gold. Then we decide to move the sphere closer and closer to this plate.

Now you see this plate is designed so it can rotate around this axis, right? And so now, if I approach this here, there will be a Casimir force, an attractive Casimir force. So the sphere, as it gets close, will pull up, and you have a seesaw effect, right? So now, how do we measure the force? We show this force kind of in a colorful way by this here, by measuring this tiny rotation angle. This is an angle which is less than one millionth of a degree.

So we have to measure it by very sophisticated technique, by electrical method. So we measure this Casimir force between a gold sphere and a metalized gold plate, as we vary the distance between the two. And this is the first part of the story. Then, I started to think, “Now, if I change materials, I change the shape, and I can design quantum fluctuation.”

Because this quantum fluctuation of metal matter depends not on the material. Say if you have gold, silver, other material changes, they depend on the shape. And they depend also on what is between the two materials.

So if you somehow put a liquid between the sphere and the plate, things change. Suppose you take two metals and you put them inside the fluid. Now you have two metals separated by fluid. So this is shown here. So we did an experiment. Essentially, we lower the sphere of gold towards a gold plate inside the fluid. It is not important what the fluid is.

In this case, the Casimir force is always an attractive force. If you change the lower plate from gold to silica. Silica is like a transparent glass; in fact, it is used in chips all over. It’s a very common material, silica. And you keep the same liquid.

Now quantum mechanics tells us that this force becomes repulsive. See, what we measured is this repulsive force. We did not demonstrate yet quantum levitation, but the editor and the reviewers of “Nature” were so excited about it and they said, “We want to put this on every cover, so you can also put what you want to do next, what your vision is.” A type of levitation many are familiar with is magnetic levitation, and superconductive levitation forces have already been successfully applied in high speed Maglev trains in Europe and the Far East. Now I cannot make Maglev trains because it is so weak, the force. But this can be very important for nano-technology. If you make chips smaller and smaller with mobile parts and the parts become closer and closer, at some point they can stick together quantum mechanically.

Our vision is we can use this quantum levitation due to the repulsive Casimir force to keep parts away from each other. So if you like, the fluids here are like a quantum mechanical lubricant. Super lubricant is what some people have called it. So the idea is we can use this subtle quantum mechanics due to fluctuation to try to eliminate static friction – stiction – in future nano-mechanical devices.

Our appreciation to you, Dr. Capasso, for your insight and vision and for giving us an overview of your research on the intricacies of the Casimir effect and your development of quantum devices. We look forward to more good news as you and your team explore the many wonders in our universe.

Blessed viewers, thank you for your company today on Science and Spirituality. Coming up next is Words of Wisdom, after Noteworthy News. Please stay tuned to Supreme Master Television for more constructive programs. We’ll see you next time.