All-optical pulse generating and amplifying system

Details All-optical pulse generating and amplifying system All-optical pulse generating and amplifying system

1999-03-22

2001-08-14

Tarcza, Thomas H. (Department: 3662)

Optical: systems and elements

Optical amplifier

Bistable

C372S030000

Reexamination Certificate

active

06275327

ABSTRACT:

DEDICATORY CLAUSE
The invention described herein may be manufactured, used and licensed by or for the Government for governmental purposes without the payment to us of any royalties thereon.
BACKGROUND OF THE INVENTION
The spatio-temporal dynamics of non-linear systems includes many examples of chaotic behavior interspersed with regular rhythmic activity. A simple system of this type is a pair of coupled oscillators in which one oscillator, itself driven by an external source, excites the second oscillator which, in turn, attempts to inhibit the first oscillator. The competitive interaction can generate a rhythmic behavior which, at one extreme, is a variable-rate train of sharp spike-like pulses and, at the other extreme, is a quasi steady-state balance that may be used for amplification of the original input signal emitted by the external source. The two extremes of the rhythmic behavior are reached by varying the temporal response and the nonlinearity of response in the two coupled oscillators.
An example of a system for generating a series of pulses is a biological neuron which may be called an integrate-and-fire pulse generator. The neuron is usually modeled as a leaky capacitor which shorts out when its voltage reaches a critical fixed threshold, then, after the burst of current (i.e. the pulse), self-repairs the short and begins to recharge. The self-repair effect is also seen in an oil-filled capacitor. The time period between pulses depends on the strength of the externally-applied charging input. The integrate-and-fire mechanism has been implemented in many electronic designs.
Optical non-linear systems are more difficult to fabricate because of two fundamental facts. First, light intensity is a positive-definite physical quantity. Unlike electronic voltage which can be either positive or negative, light intensity can only be positive or zero. Second, photons can be created and destroyed at will in optical systems whereas electrons are conserved in electronic systems. The nonlinear optical effects in materials are primarily due to the dependence of the electrical susceptibility on the electric field of the incident optical wave. For instance, zeroth order gives birefringence, first order gives photoelectrons and third order exhibits photorefractive effects.
Hence, prior art methods of generating pulses of light required the use of a hybrid system that combined some electronics and some optics.
SUMMARY OF THE INVENTION
In the all-optical pulse generating and amplifying system, a phosphor is excited by input light of a first wavelength and, in response, emits light of a second wavelength. The light emitted by the phosphor illuminates a bistable element until, at a pre-fixed intensity of the phosphor-emitted light, the bistable element reversibly switches from non-transmissive state to transmissive state. This allows the exit of the light (also of first wavelength) that is emitted by an output light source as light pulse output of the system. An inhibitory light also passes through the bistable element during its transmissive state and quenches the phosphor light emission, thereby resulting in the return of the bistable element to its non-transmissive state and re-starting the process toward the next transmissive state. By gating the intensity (via selected non-linearity of the bistable element) of the light output in proportion to the intensity of the input light, the system can also function as an amplifier.


REFERENCES:
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patent: 06/110093 (1994-04-01), None
patent: 06310797-A (1994-04-01), None
Paradisi, “Performance Analysis of an all-optical gate using a Multisectiont ravelling wave amplifier”, IEE Proceedings-J, vol. 139, No. 1, Feb. 19992, pp. 42-49.

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