Q:

Can we change a photon's frequency in mid-air?

Can we have a light source emitting photons in the infrared range and after, lets say, 5 meters, these photons become a photon in the x-ray range?
The only way I know we can change a photon's frequency after its creation is through the redshift effect.
But can we do this somehow?
EDIT: Please forgive me for using the "mid-air" expression. Vacuum was what I meant or better yet: "colloquially to mean while in flight".
EDIT 2: Let me rephrase this question in another way.
I have a light bulb above the ceiling. If I look at that light bulb I see no light, unless I am at 5 meters from it. Meaning that in a distance < 5m the light emitted is infrared, in a distance >5m the light emitted is within the visible range.
This would be interesting to help in tumor ablation inside the human body using high radiation doses but very focused and that would only turn lethal in a specific part inside the body. For example in a brain tumor in the middle of the brain, I would like to burn it with light, but without burning the surrounding tissues, like the skin, skull and the brain around the tumor.
For this photons would have to be in a frequency that would not interact with the human body, until they reached the tumor, where their frequency would change somehow and make them interact with the tumor cells, killing/burning them.
The advantage of this procedure would be high precision, the ability to reach regions of the brain that couldn't be reached before, and the ability to avoid opening the human skull.
EDIT 3: Another interesting application of this would be to hide ceiling lamps above the ceiling, having the light crossing the ceiling bricks in a low frequency (like radio waves do) and then below the ceiling brick they would turn into visible light and lit the room. So at the first glance, we would have a lit room with no lamps in it lol.
Is this possible?
EDIT 4: With sound waves we can overlap them (focusing them) and create more energetic waves. Since light also behaves like a wave, could we focus photons to one single point, adding up their energies and for example with two low energy photons create a more energetic one?

A:

To my knowledge, other than red/blue shifting light, the frequency cannot be changed after it's emission. However you may be able to somehow set up some other material which would emit x-rays when infrared light is absorbed. Due to the nature of light and how it acts like a particle when interacting with particles so the energy gained doesn't accumulate when more light is added this will be difficult if it is possible at all.

A:

Point the light source up or down in a gravitational field and let Einstein take care of you.
Of course, if are forced to use the Earth as the source of your gravitational field you are going to need a pretty sensitive tool to measure the change in frequency. Luckily for us there is a set of of high precision sources in orbit and you can buy the corresponding high-sensitivity receivers Commercial Off-The Shelf for very reasonable prices.

