Sprinkle chicken evenly with Cajun seasoning and 1 tsp. salt. Melt 1/4 cup butter in a large nonstick skillet over medium-high heat; add chicken, and sauté 5 to 6 minutes or until done. Remove chicken.
Add bell peppers, mushrooms, and green onions to skillet, and sauté 9 to 10 minutes or until vegetables are tender and liquid evaporates.
Return chicken to skillet; stir in half-and-half, next 3 ingredients, and remaining 1/4 tsp. salt. Cook, stirring often, over medium-low heat 3 to 4 minutes or until thoroughly heated. Add linguine; toss to coat. Garnish, if desired, and serve immediately.