The bistable bahavior originating from optical nonlinear coupling between a prism and a nonlinear waveguide by using Fresnel formulas is described. Modulation and feedback curves of the optical bistable device are analyzed. Optical bistable curves at different offset angles are calculated.The results show that the smallest offset angle and threshold of the device can be determined by using this method.In prism nonlinear waveguide coupling system

as shown in Fig. 2

assuming prism the index of refraction n

0

=1

751

gap(air)

s

=100nm and its index of refraction

n

1

=1.000

waveguide thickness

w

=1400nm and its index of refraction

n

2

=

n

20

+

n

2E

I

g

=1.527 +10

-14

m

2

/W

substrate index of refraction offset angles (values of the angle shift from the incidence coupling angle) are calculated. If the offset angle △θ

<

0.18'

optical switch occurs. If the offset angle △θ

>

0.18'

optical bistable operation occurs. And the hysteresis cycle width and threshlod power increase with the increase of offset angle.