_ Department of electronics and industrial nano lasers
Investigation of coherence in the light of industrial nano lasers (coherence radiation)
Researcher and author: Dr. ( Afshin Rashid)
Note: The characteristic of the light emitted from a nano laser is its "coherence", due to which the energy loss of the beam caused by the nano laser is less than the beam caused by the lamp. Coherence means that the nano laser waves are in the same frequency and phase. move equally and as a result there is no phase difference between its waves. In this way, its beam will be very powerful.
Coherence is one of the physical properties of waves. In physics, two wave sources are perfectly coherent if they both have the same phase difference. This is an ideal characteristic of waves that causes standing interference (a standing wave is produced). In this characteristic, the power of waves to interfere with each other is measured. If the light coming out of a source is Let's divide it into two parts and create a new spring with each of them, so-called two secondary springs are made from one primary spring. Any type of (random) change in the phase that occurs in one of them is repeated exactly in the other, so the phase of the secondary springs remains constant. Two springs which are derived from a primary spring in this way and have a constant phase relationship are called coherent and the resulting light waves are called coherent waves.
For the optical wave of nano laser to be coherent, two conditions must be met. The resulting wave should be very close to single frequency. That is, the frequency splash with a small linear width. And the wave front must have a specific shape, so that it does not change with time. A wave front is a surface consisting of points with the same phase. A point light source produces a wave whose phase is constant at equal distances from the source. According to the concordance conditions, two types of concordance can be imagined.
Time coherence
Spatial coherence
temporal coherence
In terms of coherence, we stated the first condition of coherence is that the wave is single-frequency. If this condition is met, then the coherence is called temporal coherence. The meaning of time coherence is that the relative phases between two time points should be constant in a relatively long time interval. In this way, with temporal coherence, it is possible to predict the phase and amplitude after a known time interval between the initial and final evidence. If this forecasting process can be repeated some time later, then it is said that there is temporal coherence of equal magnitude and with the forecast intervals.
Spatial coherence
As the first condition of coherence, the shape of the wave front should not change with time. If this condition is met, then the resulting light is called spatial coherence. In other words, a wave is called spatially coherent when there is a constant phase difference between any two selected points on the wave front. The constant term implies a sufficient duration to perform an operation on the wavefront, such as visual observation or photography . In other words, spatial coherence requires that the relative phases between two spatial points remain constant over a relatively long time interval. In each of these cases, the longer the time interval, the greater the coherence. In order for a light source to be fully coherent, it must be spatially coherent in addition to being temporally coherent.
Conclusion :
The characteristic of the light emitted from a nano laser is its "coherence", due to which the energy loss of the beam caused by the nano laser is less than the beam caused by the lamp. Coherence means that the waves of the nano laser move in the same frequency and phase. and as a result there is no phase difference between its waves. In this way, its beam will be very powerful.
Researcher and author: Dr. ( Afshin Rashid)
Specialized doctorate in nano-microelectronics